14.2. Creating tasks

Tasks on the client (tablet, desktop) are written in C++. All client tasks are classes that inherit from the Task class, define their database structure, and implement an editor() function that implements the task itself. Typically, one of two methods is used:

  • Simple tasks create a Questionnaire object and use questionnaire elements (described below) to capture user responses. Arbitrary logic is possible, both in terms of what constitutes “enough information” and in terms of page flow (see e.g. the CIS-R).

  • Complex tasks create a graphics widget and manipulate Qt graphics objects directly, giving arbitrary power. Examples include the IDED3D task.

On the server, a single Python class represents the task. It must define its database structure and provide an HTML view on the data (used for the HTML and PDF representations). More or less everything else is optional, but tasks may provide numerical summary information (for trackers) or customize their clinical text views.

14.2.1. Questionnaire elements

Programmers can embed arbitrary logic in a task. Several elements are available; all inherit from QuElement. Elements are grouped into pages (QuPage). Display/sound

These elements are primarily for static display (though, for example, the programmer can manipulate the contents of static text dynamically).

  • QuAudioPlayer. Allows sounds to be played.

  • QuBackground. Widget that is styled (via CSS) to have a colour. Used to create striping background effects for custom tables (etc.).

  • QuHeading. Subclass of QuText; displays headings.

  • QuHorizontalLine. A horizontal rule or line.

  • QuImage. A static image.

  • QuSpacer. A fixed-size spacer.

  • QuText. Static text. User input

  • QuBoolean. An element to control a single boolean (0/1/NULL) field. It may display text or an image. The text may appear as a button or with an adjacent widget. Some possible appearances:

    • Unselected (NULL): check_unselected or Option

    • Unselected (NULL) and required: check_unselected_required or Option

    • False: check_false_black or check_false_red or Option

    • True: check_true_black or check_true_red or Option

  • QuButton. A button, used to execute arbitrary code.

  • QuCanvas. A canvas for sketching, which can take a default or background image.

  • QuCountdown. A countdown timer.

  • QuDateTime. Date/time input method.

  • QuDiagnosticCode. Allows searching and selection of diagnostic codes using a recognized system (e.g. ICD-10).

  • QuLineEdit. One-line text editor. (For a bigger version, see QuTextEdit.)

  • QuLineEditDouble. A one-line editor for a floating-point number, allowing constraints.

  • QuLineEditInteger. A one-line editor for an integer (C++ 32-bit int), allowing constraints.

  • QuLineEditLongLong. A one-line editor for a large (64-bit) signed integer, allowing constraints.

  • QuLineEditNHSNumber. A one-line editor for an NHS number, with validation.

  • QuLineEditULongLong. A one-line editor for a large unsigned integer, allowing constraints. (Note that the CamCOPS client generally avoids unsigned 64-bit integers, because SQLite3 doesn’t have it as one of its core data types; see https://www.sqlite.org/datatype3.html.)

  • QuMcq. A simple 1-from-many or multiple-choice question (MCQ), with a range of layout and visual options.

    • Unselected: radio_unselected or Option

    • Unselected and a response is required: radio_unselected_required or Option

    • Selected: radio_selected or Option

  • QuMcqGrid. An MCQ specialized to operate in a grid, with lots of questions having a common set of possible answers.

  • QuMcqGridDouble. A specialized MCQ with a double grid (lots of questions having a common pair of sets of possible answers; e.g. for each question, pick one from A/B/C and pick one from X/Y/Z).

  • QuMcqGridSingleBoolean. Another specialized MCQ; as for QuMcqGrid but with an additional Boolean variable per question (e.g. for each question, pick one of absent/mild/moderate/severe, and tick if distressing).

  • QuMultipleResponse. An n-from-many (multiple response) question.

    • Unselected: check_unselected or Option

    • Unselected and more responses required: check_unselected_required or Option

    • Selected: check_true_red or Option

  • QuPhoto. Uses the device camera to take a photo.

  • QuPickerInline. Pick from a list of options using a spinner or similar interface.

  • QuPickerPopup. Pick from a list of options using a pop-up selector.

  • QuSpinBoxDouble. Offers a text editing box with spinbox controls, for floating-point entry.

  • QuSpinBoxInteger. Offers a text editing box with spinbox controls, for integer entry.

  • QuSlider. A slider, for discrete or continuous numerical variables.

  • QuTextEdit. An expanding editor for entering large quantities of text. (For a smaller version, see QuLineEdit.)

  • QuThermometer. A thermometer-style visual analogue scale. Layout

These elements are simply for layout:

  • QuFlowContainer. A container that flows its contents like a word processor flows words.

  • QuGridContainer. A container implementing a grid of cells, like a table.

  • QuHorizontalContainer. Arranges other elements in a horizontal row.

  • QuVerticalContainer. Arranges other elements in a vertical column.

14.2.2. Dynamic questionnaire logic, with examples

Individual task classes inherit from Task which inherits from DatabaseObject. Database objects have fields (Field objects) that are referred to by name (plus methods to load/save from the database).

Questionnaire elements automatically and dynamically reflect their field content. For example, a QuMcq object (and many other Element objects) takes a FieldRefPtr, which is a pointer to a FieldRef. A FieldRef may refer to something wholly arbitrary and transient (such as via getter/setter functions), but most typically a FieldRef refers to a field in a DatabaseObject, by field name. This system allows questionnaires to show arbitrary content but provides a simple mechanism to have one or many fields provide views onto the task’s fields.

  • A very basic example is the Irac task, which uses two QuMcq elements.

  • A basic example using QuMcqGrid is the Phq9 task.

  • An example of a slightly more complex view on data is the Bmi task. This stores mass and height in metric units, but can provide a dynamic editable view in Imperial units.

More dynamic content usually requires that the Task objects keeps some sort of reference to the questionnaire during editing. The simplest way is to keep a safe pointer to the Questionnaire (QPointer<Questionnaire> m_questionnaire) but you can keep pointers to more detailed things too. (The task will not own the Questionnaire. A QPointer is automatically set to zero when its referenced object is destroyed.)

Since FieldRef objects also maintain a mandatory flag, data input can be made conditional.

  • A reasonably simple example of this is the Icd10Depressive task. It connects the FieldRef::valueChanged signal, for each of its informative fields, to its Icd10Depressive::updateMandatory function. This function calculates whether the task is in a position to know if the patient definitely meets the criteria for depression, or definitely does not have depression by these criteria, or whether there is insufficient information to be sure. If there is insufficient information, all the relevant fields are set to mandatory, using FieldRef::setMandatory(). If it has all the information it needs, it makes the fields non-mandatory (optional). It achieves all this without storing a pointer to its Questionnaire.

  • The Cecaq3 task is a much more complicated example, mostly using this simple principle.

The display of elements can also be made conditional, in a simple way.

Elements (and pages) can have one or several string tags added to them. FieldRef objects can have hints attached to them. Both these systems allow recipients of callbacks to identify the source, without the need for a profusion of callback functions. Tags are also (and more commonly) used to set an attribute (such as being visible or mandatory) on multiple elements or field references that are conceptually related.

  • The Cape42 task uses hints to determine which question a callback is coming from. If the subject endorses a symptom, a set of further questions (frequency, distress) is made visible (and potentially mandatory), using the tag system to apply visibility. The result is that if the subject doesn’t endorse the symptom, he/she can move on without seeing the follow-up questions, but those questions appear and must be completed if the symptom is endorsed.

  • In the Ace3 task, if the subject has got all the free address recall questions right, the cued recall page shows a “Nothing to see here; move along” message. Internally, it has a m_questionnaire pointer as its only link to its Questionnaire.

  • The Bdi task switches which of three QuMcqGrid elements is shown, depending on which scale version is selected. It takes the approach of storing safe pointers to them directly.

Tasks can use callbacks with the hints and tags systems, but can of course also store safe pointers to elements or FieldRef objects.

  • The Caps task is an example of storing FieldRefPtr objects for use in callbacks.

Arbitrarily complex logic can be used with the dynamic questionnaire system. Rather than a plain Questionnaire, one can use a DynamicQuestionnaire. This takes as parameters two functions: one to make a page (given its integer index), and one to report whether or not there are more pages to go (given the integer index of the current page).

  • The Cisr task is pretty complex as questionnaires go. It implements a decision tree that includes or skips questions (pages) depending on the subject’s answers. The total number of pages depends on the subject’s answers, and the subject can browse back and forth. New pages are created and build dynamically; see Cisr::makePage() and Cisr::morePagesToGo().

14.2.3. Implementing specific elements Likert-type scales

Likert-type scales are discrete – for example,

Roses are best when red.

 Strongly    Disagree    Neutral      Agree      Strongly
 disagree                                         agree

These are fairly well suited to a QuSlider. Because asymmetry can bias the response, you probably want a slider that displays its handle in the centre when no value has been selected, and which is symmetric in terms of the colouring left/right of the handle. For example, if we code the scale above from 1 “strongly disagree” to 5 “strongly agree”, we could do this:

#include "questionnairelib/questionnaire.h"
#include "questionnairelib/qugridcontainer.cpp"
#include "questionnairelib/quslider.h"
#include "questionnairelib/qutext.h"

// ...

OpenableWidget* MyTask::editor(const bool read_only)
    const QString ROSES_FIELDNAME("roses");
    const int STRONGLY_DISAGREE = 1;
    const int DISAGREE = 2;
    const int NEUTRAL = 3;
    const int AGREE = 4;
    const int STRONGLY_AGREE = 5;

    // --------------------------------------------------------------------
    // Question
    // --------------------------------------------------------------------

    auto rose_q = new QuText("Roses are best when red.");

    // --------------------------------------------------------------------
    // Likert-style slider
    // --------------------------------------------------------------------
    // Create the horizontal slider
    QuSlider* likert_slider = new QuSlider(

    // Ticks for every interval, above and below

    // Labels
        {STRONGLY_DISAGREE, "Strongly\ndisagree"},  // or an xstring()
        {DISAGREE, "Disagree"},
        {NEUTRAL, "Neutral"},
        {AGREE, "Agree"},
        {STRONGLY_AGREE, "Strongly\nagree"},

    // Don't show the numerical value

    // Symmetry

    // --------------------------------------------------------------------
    // Grid to improve layout
    // --------------------------------------------------------------------

    // Make the scale take 70% of the screen width.
    const int MARGIN_WIDTH = 15;  // each side
    const int LIKERT_WIDTH = 70;
    auto likert_slider_grid = new QuGridContainer();
    likert_slider_grid->setColumnStretch(0, MARGIN_WIDTH);
    likert_slider_grid->setColumnStretch(1, LIKERT_WIDTH);
    likert_slider_grid->setColumnStretch(2, MARGIN_WIDTH);
    likert_slider_grid->addCell(QuGridCell(likert_slider, 0, 1));

    // --------------------------------------------------------------------
    // Page, questionnaire
    // --------------------------------------------------------------------

    auto page1 = new QuPage{rose_q, likert_slider_grid};
    page1->setTitle("Test Likert");
    auto questionnaire = new Questionnaire(m_app, {page1});
    return questionnaire;

The main disadvantage is that sliders require their handles be dragged (rather than tap-to-choose); this is part of the Qt QSlider behaviour. Clicking to the left/right moves the slider, but not all the way to the click point. This is pretty minor, though, and there are desirable aspects to it too (e.g. nudging it to the right/left is possible).

Alternatives might include:

  • a vertical QuSlider, similarly;

  • a (vertical) QuThermometer;

  • a future modification to make QuSlider tap-to-choose;

  • a future modification to make QuThermometer operate horizontally. Visual analogue scales

A visual analogue scale is continuous; for example:

Please rate something.

   Low                                             High

You can implement this with a QuSlider, as above. Use a large integer range (e.g. 0-1000) as a discrete approximation to a continuous space. (Not continuous enough for you? Pick a bigger integer range. How many pixels do you have, anyway?) Scale to your desired floating-point range as follows. (See also the example in the QOL-Basic task.) Suppose we want to represent the range 0-1 with 1000 steps (i.e. to 3dp).

#include "questionnairelib/questionnaire.h"
#include "questionnairelib/qugridcontainer.cpp"
#include "questionnairelib/quslider.h"

// ...

OpenableWidget* MyTask::editor(const bool read_only)
    const QString VAS_FIELDNAME("vas");
    const int VAS_MIN_INT = 0;  // the internal integer minimum
    const int VAS_CENTRAL_INT = 500;  // centre, for initial display
    const int VAS_MAX_INT = 1000;  // the internal integer maximum
    const double VAS_MIN = 0.0;  // the database/display minimum
    const double VAS_MAX = 1.0;  // the database/display maximum
    const int VAS_DISPLAY_DP = 3;
    const int VAS_ABSOLUTE_SIZE_CM = 10.0;
    const bool VAS_CAN_SHRINK = true;

    // --------------------------------------------------------------------
    // VAS-style slider
    // --------------------------------------------------------------------

    // Create the horizontal slider
    QuSlider* vas_slider = new QuSlider(
        fieldRef(VAS_FIELDNAME), VAS_MIN_INT, VAS_MAX_INT, 1);
    vas_slider->setConvertForRealField(true, VAS_MIN, VAS_MAX, VAS_DISPLAY_DP);

    // Ticks just at the extremes

    // Labels
        {VAS_MIN_INT, QString::number(VAS_MIN)},  // or whatever
        {VAS_MAX_INT, QString::number(VAS_MAX)},

    // Show the numerical value

    // Symmetry

    // Absolute size, if absolutely required (beware small screens -- you
    // may want the can_shrink parameter to be true for those; if the
    // screen is too small, the slider goes below the specified absolute
    // size).
    vas_slider->setAbsoluteLengthCm(VAS_ABSOLUTE_SIZE_CM, VAS_CAN_SHRINK);

    // --------------------------------------------------------------------
    // Page, questionnaire
    // --------------------------------------------------------------------

    auto page1 = new QuPage{vas_slider};
    page1->setTitle("Test VAS");
    auto questionnaire = new Questionnaire(m_app, {page1});
    return questionnaire;

Note that the use of setConvertForRealField means that your database representation will be in the desired floating-point format. Integers will only be used internally in the slider.