source: orange/docs/extend-widgets/rst/settings.rst @ 11408:c2d2400b6a90

Revision 11408:c2d2400b6a90, 25.2 KB checked in by Ales Erjavec <ales.erjavec@…>, 13 months ago (diff)

Fixes for Widgets Development documentation.

2Settings and Controls
5In the :doc:`previous section <basics>` of our tutorial we
6have just built a simple sampling widget. Let us now make this widget
7a bit more useful, by allowing a user to set the proportion of data
8instances to be retained in the sample. Say we want to design a widget
9that looks something like this:
11.. image:: dataSamplerBWidget.png
13What we added is an Options box, with a spin entry box to set the
14sample size, and a check box and button to commit (send out) any
15change we made in setting. If the check box with "Commit data on
16selection change" is checked, than any change in the sample size will
17make the widget send out the sampled data set. If data sets are large
18(say of several thousands or more) instances, we may want to send out
19the sample data only after we are done setting the sample size, hence
20we left the commit check box unchecked and press "Commit" when we are
21ready for it.
23This is a very simple interface, but there is something more to
24it. We want the settings (the sample size and the state of the commit
25button) to be saved. That is, any setting we made, after closing our
26widget (or after going out of Orange application that includes this
27widget, or after closing Orange Canvas), we want to save so that the
28next time we open the widget the settings is there as we have left
29it. There is some complication to it, as widget can be part of an
30application, or part of some schema in the Canvas, and we would like
31to have the settings application- or schema-specific.
34Widgets Settings
37Luckily, since we use the base class :obj:`OWWidget`, the settings
38will be handled just fine. We only need to tell which variables we
39will use for the settings. For Python inspired readers: these
40variables can store any complex object, as long as it is
41picklable. In our widget, we will use two settings variables, and we
42declare this just after the widget class definition.
46    class OWDataSamplerB(OWWidget):
47        settingsList = ['proportion', 'commitOnChange']
48        def __init__(self, parent=None, signalManager=None):
50Any setting has to be initialized, and then we need to call
51:obj:`loadSettings()` to override defaults in case we have used
52the widget before and the settings have been saved::
54    self.proportion = 50
55    self.commitOnChange = 0
56    self.loadSettings()
58Now anything we do with the two variables (:obj:`self.proportion` and
59:obj:`self.commitOnChange`) will be saved upon exiting our
60widget. In our widget, we won't be setting these variables directly,
61but will instead use them in conjunction with GUI controls.
64Controls and OWGUI
67Now we could tell you how to put different Qt controls on the
68widgets and write callback functions that set our settings
69appropriately. This is what we have done before we got bored with it,
70since the GUI part spanned over much of the widget's code. Instead, we
71wrote a library called OWGUI (I never liked the name, but could never
72come up with something better). With this library, the GUI definition
73part of the options box is a bit dense but rather very short::
75    box = OWGUI.widgetBox(self.controlArea, "Info")
76    self.infoa = OWGUI.widgetLabel(box, 'No data on input yet, waiting to get something.')
77    self.infob = OWGUI.widgetLabel(box, '')
79    OWGUI.separator(self.controlArea)
80    self.optionsBox = OWGUI.widgetBox(self.controlArea, "Options")
81    OWGUI.spin(self.optionsBox, self, 'proportion', min=10, max=90, step=10,
82               label='Sample Size [%]:', callback=[self.selection, self.checkCommit])
83    OWGUI.checkBox(self.optionsBox, self, 'commitOnChange', 'Commit data on selection change')
84    OWGUI.button(self.optionsBox, self, "Commit", callback=self.commit)
85    self.optionsBox.setDisabled(1)
87We are already familiar with the first part - the Info group
88box. To make widget nicer, we put a separator between this and Options
89box. After defining the option box, here is our first serious OWGUI
90control. Called a :obj:`spin`, we give it place where it is
91drawn (:obj:`self.optionsBox`), and we give it the widget object
92(:obj:`self`) so that it knows where the settings and some other
93variables of our widget are.
95Next, we tell the spin box to be
96associated with a variable called :obj:`proportion`. This simply
97means that any change in the value the spin box holds will be directly
98translated to a change of the variable
99:obj:`self.proportion`. No need for a callback! But there's
100more: any change in variable :obj:`self.proportion` will be
101reflected in the look of this GUI control. Say if there would be a
102line :obj:`self.proportion = 70` in your code, our spin box
103control would get updated as well. (I must admit I do not know if you
104appreciate this feature, but trust me, it may really help prototyping
105widgets with some more complex GUI.
107The rest of the OWGUI spin box call gives some parameters for the
108control (minimum and maximum value and the step size), tells about the
109label which will be placed on the top, and tells it which functions to
110call when the value in the spin box is changed. We need the first
111callback to make a data sample and report in the Info box what is the
112size of the sample, and a second callback to check if we can send this
113data out. In OWGUI, callbacks are either references to functions, or a
114list with references, just like in our case.
116With all of the above, the parameters for the call of
117:obj:`OWGUI.checkBox` should be clear as well. Notice that this
118and a call to :obj:`OWGUI.spin` do not need a parameter which
119would tell the control the value for initialization: upon construction,
120both controls will be set to the value that is pertained in the
121associated setting variable.
123That's it. Notice though that we have, as a default, disabled all
124the controls in the Options box. This is because at the start of the
125widget, there is no data to sample from. But this also means that when
126process the input tokens, we should take care for enabling and
127disabling. The data processing and token sending part of our widget
128now is::
130    def data(self, dataset):
131        if dataset:
132            self.dataset = dataset
133            self.infoa.setText('%d instances in input data set' % len(dataset))
134            self.optionsBox.setDisabled(0)
135            self.selection()
136            self.commit()
137        else:
138            self.send("Sampled Data", None)
139            self.optionsBox.setDisabled(1)
140            self.infoa.setText('No data on input yet, waiting to get something.')
141            self.infob.setText('')
143    def selection(self):
144        indices = orange.MakeRandomIndices2(p0=self.proportion / 100.)
145        ind = indices(self.dataset)
146        self.sample =, 0)
147        self.infob.setText('%d sampled instances' % len(self.sample))
149    def commit(self):
150        self.send("Sampled Data", self.sample)
152    def checkCommit(self):
153        if self.commitOnChange:
154            self.commit()
156You can now also inspect the :download:`complete code <>`
157of this widget. To distinguish it with a widget we have developed in the
158previous section, we have designed a special
159:download:`icon <DataSamplerB.png>` for it. If you wish to test is
160widget in the Orange Canvas, put its code in the Test directory we
161have created for the previous widget, update the Canvas registry, and
162try it out using a schema with a File and Data Table widget.
164.. image:: schemawithdatasamplerB.png
167Well-behaved widgets remember their settings - the state of their
168checkboxes and radio-buttons, the text in their line edits, the
169selections in their combo boxes and similar. These settings are even
170maintained across sessions. This document describes the Orange's
171methods that take care of that.
173Orange doesn't really save the state of the controls but instead
174saves the value of the corresponding attributes. For a check box there
175should be a corresponding widget's attribute recording the check box's
176state so that when the user changes a check box, the attribute changes
177and vice-versa. Although you can create such a link manually, you
178should always use the module :doc:`OWGUI <owgui.rst>` instead;
179for instance, for a check box, use :obj:`OWGUI.checkBox` and not
180simply the Qt's :obj:`QCheckBox`.
182The settings fall into two groups. Some of them do not depend on
183the data, while other are context-dependent. For the first to be saved
184properly, you only need to list them in the :obj:`settingsList`
185in the widget definition, as already described :doc:`elsewhere <settings.rst>`
188Context dependent settings
191Context dependent settings usually depend upon the attributes that
192are present in the data set domain. For instance, the scatter plot
193widget contains settings that specify the attributes for x and y axis,
194and the settings that define the color, shape and size of the examples
195in the graph. An even more complicated case is the widget for data
196selection with which one can select the examples based on values of
197certain attributes. Before applying the saved settings, these widgets
198needs to check their compliance with the domain of the actual data
199set. To be truly useful, context dependent settings needs to save a
200setting configuration for each particular data set used. That is, when
201given a particular data set, it has to select the saved settings that
202is applicable and matches best currently used data set.
204Saving, loading and matching contexts is taken care of by context
205handlers. Currently, there are only two classes of context handlers
206implemented. The first one is the abstract :obj:`ContextHandler`
207and the second one is :obj:`DomainContextHandler` in which the
208context is defined by the data set domain and where the settings
209contain attribute names. The latter should cover most of your needs,
210while for more complicated widgets you will need to derive a new
211classes from it. There may even be some cases in which the context is
212not defined by the domain, in which case the
213:obj:`ContextHandler` will be used as a base for your new
216Contexts need to be declared, opened and closed. Opening and
217closing usually takes place (in the opposite order) in the function
218that handles the data signal. This is how it looks in the scatter plot
219(the code is somewhat simplified for clarity). ::
221    def cdata(self, data, clearResults = 1):
222        self.closeContext()
224        exData =
225 = data
226        self.graph.setData(data)
227        self.graph.insideColors = None
228        self.graph.clusterClosure = None
230        self.initAttrValues()
232        self.openContext("", data)
234        self.updateGraph()
235        self.sendSelections()
237In general, the function should go like this.
239* Do any clean-up you need, but without clearing any of the settings that need to be saved. Scatter plot needs none.
240* Call :obj:`self.closeContext`; this ensures that all the context dependent settings (e.g. attribute names from the list boxes) are remembered.
241* Get the data (or whatever you do) and set the controls to some defaults as if there were no context retrieving mechanism. Scatter plot does it by calling :obj:`initAttrValues()` which assigns the first two attributes to the x and y axis and the class attribute to the color. At this phase, you shouldn't call any functions that depend on the settings, such as drawing the graph.
242* Call :obj:`self.openContext` (more about the arguments later). This will search for a suitable context and assign the controls new values if one is found. If there is no saved context that can be used, a new context is created and filled with the default values that were assigned at the previous point.
243* Finally, adjust the widget according to the retrieved controls. Scatter plot now plots the graph by calling :obj:`updateGraph`.
246:obj:`closeContext` has an argument, the name of the context. If omitted (like above), the default name (:obj:`""`) is used. When opening the context, we give the name and some arguments on which the context depends. In case of :obj:`DomainContextHandler`, which scatter plot uses, we can give it a domain or any object that has a field :obj:`domain` containing a domain. Whether a saved context can be reused is judged upon the presence of attributes in the domain.
248If the widget is constructed appropriately (that is, if it strictly uses OWGUI controls instead of the Qt's), no other administration is needed to switch the context.
250Except for declaring the context settings, that is. Scatter plot has this just below the :obj:`settingsList`::
252    contextHandlers = {"": DomainContextHandler("",
253      [("attrX", DomainContextHandler.Required),
254       ("attrY", DomainContextHandler.Required),
255       ("attrLabel", DomainContextHandler.Optional),
256       ("attrShape", DomainContextHandler.Optional),
257       ("attrSize", DomainContextHandler.Optional)])}
259:obj:`contextHandlers` is a dictionary whose keys are contexts' names. Each widget can have multiple contexts; for an unrealistic example, consider a scatter plot which gets two data sets and uses one attribute from the first for the x axis, and an attribute from the other for y. Since we won't see this often, the default name for a context is an empty string.
261The values in the dictionary are context handlers. Scatter plot declares that it has a DomainContextHandler with name "" (sorry for the repetition) with attributes "attrX", "attrY", "attrLabel", "attrShape" and "attrSize". The first two are required, while the other three are optional.
264Using :obj:`DomainContextHandler`
267What we said above is not exactly
268true. :obj:`DomainContextHandler.Required` is the default flag,
269so :obj:`("attrX", DomainContextHandler.Required)` can be
270replaced by simply :obj:`"attrX"`. And the latter three have the
271same flags, so they can be grouped into :obj:`(["attrLabel",
272"attrShape", "attrSize"], DomainContextHandler.Optional)`. So
273what scatter plot really says is ::
275    contextHandlers = {"": DomainContextHandler("", [
276       "attrX", "attrY",
277       (["attrLabel", "attrShape", "attrSize"], DomainContextHandler.Optional)])}
279What do "optional" and "required" mean? Say that you used the
280scatter plot on the data with attributes A, B, C and D; A and B are
281used for the x and y axis and D defined the colors of examples. Now
282you load a new data with attributes A, B, E, and F. The same context
283can be used - A and B will again be shown on x and y axis and the
284default (the one set by :obj:`self.initAttrValues`) will be used
285for the color since the attribute D is missing in the new data. Now
286comes the third data set, which only has attributes A, D and E. The
287context now can't be reused since the attribute used for the
288*required* :obj:`attrY` (the y axis) is missing.
290OK, now it is time to be a bit formal. As said,
291:obj:`contextHandlers` is a dictionary and the values in it need
292to be context handlers derived from the abstract class
293:obj:`ContextHandler`. The way it is declared of course depends
294upon its constructor, so the above applies only to the usual
297DomainContextHandler's constructor has the following arguments
300The name of the context; it should consist of letters and digits (it is used as a prt of a variable name). In case the widget has multiple contexts, they should have unique names. In most cases there will be only one context, so you can leave it empty.
303The names of the attributes to be saved and the corresponding flags. They are described in more details below.
306states that when the context doesn't match perfectly, that is, unless the domain is exactly the same as the domain from which the context was originally created, :obj:`openContext` shouldn't reuse a context but create a copy of the best matching context instead. Default is :obj:`True`.
309tells whether the contexts that do not match perfectly (see above) should be used or not. Default is :obj:`True`.
312tells whether imperfect contexts match at all or not (this flag is somewhat confused with :obj:`loadImperfect`, but it may come useful some day. Default is :obj:`True` again.
315tells whether instances of this widget should have a shared list of contexts (default). The alternative is that each keeps its own list; each individual list is merged with the global when the widget is deleted from the canvas (or when the canvas is closed). This setting only applies to canvas, while in saved applications widgets always have separate settings lists.
318To keep the size of the context file small, settings for domains exceeding a certain number of attributes are not pickled. Default is 100, but you can increase (or decrease this) if you need to.
321The truly interesting argument is :obj:`fields`. It roughly corresponds to the
322:obj:`settingsList` in that each element specifies one widget attribute to be
323saved. The elements of :obj:`fields` can be strings, tuples and/or instances of
324:obj:`ContextField` (whatever you give, it gets automatically converted to the
325latter). When given as tuples, they should consist of two elements, the field
326name (just like in :obj:`settingsList`) and a flag. Here are the possible flags:
328* :obj:`DomainContextHandler.Optional`, :obj:`DomainContextHandler.SelectedRequired` and :obj:`DomainContextHandler.Required` state whether the attribute is optional or required, as explained above. Default is :obj:`Required`. :obj:`DomainContextHandler.SelectedRequired` is applicable only if the control is a list box, where it means that the attributes that are selected are required while the other attributes from the list are not.
329* :obj:`DomainContextHandler.NotAttribute` the setting is not an attribute name. You can essentially make a check box context dependent, but we very strongly dissuade from this since it can really confuse the user if some check boxes change with the data while most do not.
330* :obj:`DomainContextHandler.List` tells that the attribute corresponds to a list box.
333Flags can be combined, so to specify a list in which all attributes
334are required, you would give :obj:`DomainContextHandler.List +
335DomainContextHandler.Required`. Since this combination is
336common, :obj:`DomainContextHandler.RequiredList` can be used
339There are two shortcuts. The default flag is
340:obj:`DomainContextHandler.Required`. If your attribute is like
341this (as most are), you can give only its name instead of a
342tuple. This is how :obj:`"attrX"` and :obj:`"attrY"` are
343given in the scatter plot. If there are multiple attributes with the
344same flags, you can specify them with a tuple in which the first
345element is not a string but a list of strings. We have seen this trick
346in the scatter plot, too.
348But the tuples are actually a shortcut for instances of
349:obj:`ContextField`. When you say :obj:`"attrX"` this is actually
350:obj:`ContextField("attrX", DomainContextHandler.Required)` (you should
351appreciate the shortcurt, right?). But see this monster from widget "Select
352Attributes" (file
354    contextHandlers = {"": DomainContextHandler("",
355        [ContextField("chosenAttributes",
356                       DomainContextHandler.RequiredList,
357                       selected="selectedChosen", reservoir="inputAttributes"),
358         ContextField("classAttribute",
359                       DomainContextHandler.RequiredList,
360                       selected="selectedClass", reservoir="inputAttributes"),
361         ContextField("metaAttributes",
362                       DomainContextHandler.RequiredList,
363                       selected="selectedMeta", reservoir="inputAttributes")
364    ])}
367:obj:`ContextField`'s constructor gets the name and flags and a list of
368arguments that are written directly into the object instance. To follow the
369example, recall what Select Attributes looks like: it allows you to select a
370subset of attributes, the class attribute and the meta attributes that you
371want to use; the attributes in the corresponding three list boxes are stored
372in the widget's variables :obj:`chosenAttributes`, :obj:`classAttribute`
373and :obj:`metaAttributes` respectively. When the user selects some attributes
374in any of these boxes, the selection is stored in :obj:`selectedChosen`,
375:obj:`selectedClass` and :obj:`selectedMeta`. The remaining attributes
376- those that are not in any of these three list boxes - are in the leftover
377listbox on the left-hand side of the widget, and the content of the box is
378stored in the widget's variable :obj:`inputAttributes`.
380The above definition tells that the context needs to store the contents of
381the three list boxes by specifying the corresponding variables; the list of
382attributes is given as the name of the field and the list of selected
383attributes is in the optional named attribute :obj:`selected`. By
384:obj:`reservoir` we told the context handler that the attributes are taken
385from :obj:`inputAttributes`. So, when a context is retrieved, all the
386attributes that are not in any of the three list boxes are put into
389Why the mess? Couldn't we just store :obj:`inputAttributes` as the fourth
390list box? Imagine that the user first loads the data with attributes A, B,
391C, D, E and F, puts A, B, C in chosen and D in class. E and F are left in
392:obj:`inputAttributes`. Now she loads another data which has attributes A,
393B, C, D, E, and G. The contexts should match (the new data has all the
394attributes we need), but :obj:`inputAttributes` should now contain E and
395G, not E and F, since F doesn't exist any more, while G needs to be made
398You can use :obj:`ContextField` (instead of tuples and strings) for
399declaring any fields, but you will usually need them only for lists or,
400maybe, some complicated future controls.
404Defining New Context Handlers
407Avoid it if you can. If you can't, here's the list of the methods you may need to implement. You may want to copy as much from the :obj:`DomainContextHandler` as you can.
411Has the same arguments as the :obj:`DomainContextHandler`'s, except for the :obj:`fields`.
414Creates and returns a new context. In :obj:`ContextHandler` is returns an instance of :obj:`Context`; you probably won't need to change this.
417The method is given a widget and some additional arguments based on which the contexts are compared. In case of :obj:`DomainContextHandler` this is a domain. There can be one or more such arguments. Note that the method :obj:`openContext` which we talked about above is a method of :obj:`OWBaseWidget`, while here we describe a method of context handlers. Actually, :obj:`OWBaseWidget(self, contextName, *args)` calls the context handler's, passing it's :obj:`self` and :obj:`*args`.
419It needs to find a matching context and copy its settings to the widget or construct a new context and copy the settings from the widget. Also, when an old context is reused, it should be moved to the beginning of the list. :obj:`ContextHandler` already defines this method, which should usually suffice. :obj:`DomainContextHandler` adds very little to it.
422Copies the settings from the widget by calling :obj:`settingsFromWidget`. You probably won't need to overwrite it.
425The method is called by :obj:`openContext` to find a matching context. Given an existing context and the arguments that were given to :obj:`openContext` (for instance, a domain), it should decide whether the context matches or not. If it returns 2, it is a perfect match (e.g. domains are the same). If it returns 0, the context is not applicable (e.g. some of the required attributes are missing). In case it returns a number between 0 and 1 (excluding 0), the higher the number the better the match. :obj:`openContext` will use the best matching context (or the perfect one, if found).
428Copy the settings to and from the widget.
431This function is called by the widget's :obj:`__setattr__` each time any widget's variable is changed to immediately synchronize the context with the state of the widget. The method is really needed only when :obj:`syncWithGlobal` is set. When the context is closed, :obj:`closeContext` will save the settings anyway.
434Given an existing context, it prepares and returns a copy. The method is optional; :obj:`copy.deepcopy` can be used instead.
438Saving and loading settings
441Settings can be saved in two different places. Orange Canvas save
442settings in .ini files in directory
443Orange/OrangeWidgets/widgetSettings. Each widget type has its separate
444file; for instance, the scatter plot's settings are saved in
445:obj:`ScatterPlot.ini`. Saved schemas and applications save
446settings in .sav files; the .sav file is placed in the same directory
447as the schema or application, has the same name (except for the
448extension) and contains the settings for all widgets in the
451Saving and loading is done automatically by canvas or the
452application. In a very rare case you need it to run these operations
453manually, the functions involved are :obj:`loadSettings(self, file =
454None)`, :obj:`saveSettings(self, file = None)`,
455:obj:`loadSettingsStr(self, str)`,
456:obj:`saveSettingsStr(self)`. The first two load and save from
457the file; if not given, the default name (widget's name +
458:obj:`.ini`) is used. They are called by the canvas, never by a
459schema or an application. The last two load and save from a string and
460are used by schemas and applications. All the functions are defined as
461methods of :obj:`OWBaseWidget`, which all other widgets are
462derived from.
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