DVX_GUI/listhelp

listhelp -- Shared List/Dropdown Helper Library

Shared infrastructure for list and dropdown widgets, built as listhelp.lib (DXE3 module). Provides dropdown arrow drawing, item measurement, keyboard navigation, popup rectangle calculation, and popup list painting.

Used by: Dropdown, ComboBox, ListBox, ListView, TreeView.

API Reference

Dropdown Arrow Glyph

void widgetDrawDropdownArrow(DisplayT *d, const BlitOpsT *ops,
    int32_t centerX, int32_t centerY, uint32_t color);

Draws the small downward-pointing triangle glyph used on dropdown buttons.

Item Measurement

int32_t widgetMaxItemLen(const char **items, int32_t count);

Scans an array of item strings and returns the length of the longest one. Used to size dropdown popups and list columns to fit their content.

Keyboard Navigation

int32_t widgetNavigateIndex(int32_t key, int32_t current,
    int32_t count, int32_t pageSize);

Maps arrow key presses to index changes for list navigation. Handles Up, Down, Home, End, PageUp, and PageDown. Returns the new selected index, clamped to valid range.

Popup Rectangle Calculation

void widgetDropdownPopupRect(WidgetT *w, const BitmapFontT *font,
    int32_t contentH, int32_t itemCount,
    int32_t *popX, int32_t *popY,
    int32_t *popW, int32_t *popH);

Computes the screen rectangle for a dropdown popup overlay. Positions the popup below the widget (or above if there is not enough room below). Limits height to DROPDOWN_MAX_VISIBLE items.

Popup List Painting

void widgetPaintPopupList(DisplayT *d, const BlitOpsT *ops,
    const BitmapFontT *font, const ColorSchemeT *colors,
    int32_t popX, int32_t popY, int32_t popW, int32_t popH,
    const char **items, int32_t itemCount,
    int32_t hoverIdx, int32_t scrollPos);

Renders the popup overlay list with items, selection highlight, scroll position, and beveled border. Used by Dropdown and ComboBox for their popup overlays.

Constants

Name	Value	Description
DROPDOWN_BTN_WIDTH	16	Width of dropdown arrow button area
DROPDOWN_MAX_VISIBLE	8	Maximum visible items in popup list

Exported Symbols

Matches prefixes: _widgetDraw*, _widgetDropdown*, _widgetMax*, _widgetNavigate*, _widgetPaint*.

Files

File	Description
listHelp.h	Public API header
listHelp.c	Complete implementation
Makefile	Builds bin/libs/listhelp.lib + dep file

Build

make            # builds bin/libs/listhelp.lib + listhelp.dep
make clean      # removes objects, library, and dep file

Depends on: libtasks.lib, libdvx.lib (via listhelp.dep).