User Interface / Accessibility

Cataclysm: Dark Days Ahead uses ncurses, or in the case of the tiles build, an ncurses port, for user interface. Window management is achieved by ui_adaptor, which requires a resizing callback and a redrawing callback for each UI to handle resizing and redrawing. A migration effort is underway for user interface code to be moved to ImGui, which uses SDL on the tiled build, and ncurses on non-tiled Linux builds.

Some good examples of the usage of ui_adaptor can be found within the following files:

  • string_input_popup in string_input_popup.cpp, specifically in string_input_popup::query_string()
  • Messages::dialog in messages.cpp

Details on how to use ui_adaptor can be found within ui_manager.h.

New user interfaces should be coded using ImGui. ImGui-backed windows are created using cataimgui::window as a base, see cata_imgui.h/cpp. cataimgui::window still uses ui_adaptor but it is handled internally. cataimgui::window handles creating the ImGui window itself, but any widgets (i.e. text boxes, tables, input fields) must be created using the correct function under the ImGui namespace. Examples of creating any ImGui widget can be found in src/third-party/imgui_demo.cpp

Good examples of implementating an ImGui-based UI in cataclysm:

  • demo_ui a minimal example (about 80 lines) in main_menu.cpp added in PR#72171
  • query_popup and static_popup in popup.h/cpp, specifically query_popup_impl which is a private implementation class used by the aforementioned classes.
  • keybindings_ui in input.cpp, which is a private implementation class used by input_context::display_menu().

SDL version requirement of the tiles build

Some functions used by this project require SDL 2.0.6, and the actual version requirement might be higher. While using a newer version is optional, new versions add several hints that are used to fix some incorrect behaviors of older SDL versions. These hints and the minimum SDL version requirements can be found within InitSDL in sdltiles.cpp. For example, SDL 2.0.20 is required for IME candidate list to show correctly on Windows, and SDL 2.0.22 is required for long IME composition text to show correctly.

Compatibility with screen readers

There are people who use screen readers to play Cataclysm DDA. There are several things to keep in mind when checking the user interface for compatibility with screen readers. These include:

  1. Screen reader mode:

An option (“SCREEN_READER_MODE”) has been added where the user can indicate that they are using a screen reader. If a change to the UI to optimize for screen readers would be undesirable for other users, consider checking against “SCREEN_READER_MODE”, and including the change when true.

  1. Text color:

Text color is not announced by screen readers. If key information is only communicated to the player through text color, that information will not be available to players using screen readers. For example, a simple uilist where some options have been disabled:

----------------------------------------------------------------------------
|Execute which action?                                                     |
|--------------------------------------------------------------------------|
|<color_c_green>1</color> <color_c_light_gray>Cut up an item</color>       |
|<color_c_green>f</color> <color_c_light_gray>Start a fire quickly</color> |
|<color_c_dark_gray>h Use holster</color>                                  |
----------------------------------------------------------------------------

A screen reader user will only know that “Use holster” is unavailable when they attempt to use it. When presenting information, consider hiding inaccessible options and adding text to confirm information conveyed by text color. As an example, the display of food spoilage status:

<color_c_light_blue>Acorns (fresh)</color>

<color_c_yellow>Acorns (old)</color>
  1. Cursor placement:

In general, screen readers will start reading where the program has set the terminal cursor. Thus, the cursor should be set to the beginning of the most important section of the UI.

The recommended way to place the cursor is to use ui_adaptor. This ensures the desired cursor position is preserved when subsequent output code changes the cursor position. You can call ui_adaptor::set_cursor and similar methods at any position in a redrawing callback, and the last cursor position of the topmost UI set via the call will be used as the final cursor position. You can also call ui_adaptor::disable_cursor to prevent a UI’s cursor from being used as the final cursor position. ImGui-backed screens handle recording of the cursor automatically.

For debugging purposes, you can set the DEBUG_CURSES_CURSOR compile flag to always show the cursor in the terminal (currently only works with the curses build).

  1. Window layout:

While setting the terminal cursor position is sufficient to set things up for screen readers in many cases, there are caveats to this. Screen readers will also attempt to detect text changes. If that text change is after the terminal cursor, the screen reader may skip over text. As an example (terminal position noted by X):

XEye color: amber

changing into

XEye color: blue

The screen reader will only read the word “blue”, even though the cursor is set to start reading at “Eye”. A simple way to force the screen reader to announce key information is to add a space at the cursor position if the first letter of the displayed string has not changed. In this case,

XEye color: amber

would change into

X Eye color: blue

Another complication is if the screen reader detects text changes above the terminal cursor. As an example:

Lifestyle: underpowered
XStrength: 8

changing into

Lifestyle: weak
XStrength: 9

The screen reader will start reading at “weak” even though that’s above the terminal cursor.

Behaviour like this means that screen readers struggle with certain common UI layouts. Some examples are listed below. Examples of how to implement theses changes can be found in src/newcharacter.cpp.

Note: In all following examples, the terminal cursor is marked “X”.

4a. List with additional information at the top or bottom:

-----------------------------------------------------
|Choose type of butchery:                           |
|---------------------------------------------------|
XB Quick butchery	6 minutes                   |
|b Full butchery	39 minutes                  |
|---------------------------------------------------|
|This technique is used when you are in a hurry, but|
|still want to harvest something from the corpse.   |
-----------------------------------------------------

Figure 4ai - List with details at the bottom, current configuration

If the cursor is set at “Quick butchery”, then the screen reader will read all of the other options before getting to the description of what “Quick butchery” entails. The preferred layout in SCREEN_READER_MODE is the following:

-----------------------------------------------------
|Choose type of butchery:                           |
|---------------------------------------------------|
|                                                   |
|                                                   |
|---------------------------------------------------|
XB Quick butchery       6 minutes                   |
|This technique is used when you are in a hurry, but|
-----------------------------------------------------

Figure 4aii - List with details at the bottom, recommended "SCREEN_READER_MODE"

That is:

  1. Add the currently-selected list entry to the detail pane at the bottom, and
  2. Disable display of the list of options. The screen reader user can then scroll through the list of available options, only hearing about the details of the currently-selected option.

Hiding the list of options is necessary because if the list scrolls, the screen reader will detect that and attempt to read the list from the top. As an example:

-----------------------------------------------------
|Choose type of butchery:                           |
|---------------------------------------------------|
Yb Full butchery	39 minutes                  |
|f Field dress corpse	5 minutes                   |
|---------------------------------------------------|
XThis technique is used to properly butcher a corpse|
|and requires a rope & a tree or a butchering rack, |
-----------------------------------------------------

Figure 4aiii - List with details at the bottom with scrolling issues

When the list scrolls, the text at the top changes, and the screen reader will start reading at point Y and go through the entire list rather than the current cursor position X.

4b. List with additional information at the side:

_______________________________
|List    | Details relating to|
XItem 1  | item 1.  Lorem     |
|Item 2  | ipsum              |
|Item 3  |                    |
|Item 4  |                    |
|Item 5  |                    |
-------------------------------

Figure 4bi - List with details at the side, current configuration

In this common layout, the screen reader is unable to differentiate between the two panes, and ends up reading the list interwoven with the details of the currently-selected item. This is true whether the terminal cursor is set to the current item or to the top left of the details pane.

The recommended layout in SCREEN_READER_MODE is the following:

-------------------------------
|        | XItem 1            |
|        | Details relating to|
|        | item 1.  Lorem     |
|        | ipsum              |
|        |                    |
|        |                    |
-------------------------------

Figure 4bii - List with details at the side, recommended "SCREEN_READER_MODE"

That is:

  1. Add the currently-selected list entry to the detail pane at the side, and
  2. Disable display of the list of options.