Remaining Bugs – Hello World Titlebar & Click

Follow-up to HELLO_WORLD_LAYOUT_INVESTIGATION.md (bugs 1–5 fixed, commits 3085fed1…c2ead850). This file tracks the issues that are still open after the first round of fixes.

Bug 7 – Title text clipped to intrinsic width (flex-grow missing)

Evidence (debug data)

Titlebar container  (Node 1):  display=flex, flex-direction=row, justify-content=center
                               padding-left=78px,  used_size = (0, 0, 400, 28)
Title text          (Node 2):  formatting_context=Inline, overflow_x=hidden
                               used_size = (78.0, 6.3, 71.9, 15.5)
                               ← should be (78.0, 6.3, 322.0, 15.5)
Display-list clip:  PushClip at (78, 6.3, 71.9, 15.5) → text glyphs clipped

Fix

Add flex-grow: 1 (and optionally min-width: 0) to the title text style in build_title_style(). The text will then expand to fill the remaining space 400 − 78 = 322 px, and overflow-x: hidden + text-overflow: ellipsis will only kick in when the title is genuinely longer than the available space.

// In build_title_style(), add:
props.push(CssPropertyWithConditions::simple(
    CssProperty::const_flex_grow(LayoutFlexGrow::const_new(1)),
));
props.push(CssPropertyWithConditions::simple(
    CssProperty::const_min_width(LayoutMinWidth::const_px(0)),
));

Bug 8 – Title text color hardcoded (#4c4c4c), ignores dark mode

Fix

SoftwareTitlebar already receives the SystemStyle via from_system_style(). Store the resolved title colour in a new title_color: ColorU field and use it in build_title_style(). Fall back to #4c4c4c (light) / #e5e5e5 (dark) when SystemStyle.colors.text is None.

Bug 9 – padding_horizontal in TitlebarMetrics is never read

Fix

Either:

1. Use it – add padding_horizontal to both padding_left and padding_right in from_system_style(), OR
2. Remove it – delete the field if it is truly not needed (the button-area width already includes the optical gap).

Option 1 is preferred because macOS titlebars have an 8 px inset on the non-button side.

Bug 10 – discover_macos_style() never queries actual titlebar metrics

Fix (deferred – low priority)

On macOS, query the actual button positions at app startup through one of:

• NSWindow.standardWindowButton(.closeButton)!.frame → derive button_area_width
• NSWindow.titlebarHeight (private but widely used)
• Heuristic: NSProcessInfo.processInfo.operatingSystemVersion and a lookup table

For now the hardcoded values are correct for macOS 11–15. Mark the constants with a // Verified: macOS 11 – macOS 15 Sequoia comment so future maintainers know when to re-check.

Bug 11 – Button click does not increment counter (event delivery)

1. Debug API click does not synthesize a full LeftMouseDown → LeftMouseUp sequence – the real event pipeline may require both events (or a proper MouseUp to fire the callback).
2. on_click callback is attached via AzButton_setOnClick which may register a LeftMouseUp filter – verify that the debug API generates both MouseDown and MouseUp.
3. After Update::RefreshDom is returned, the framework must call the layout callback again – the debug API may not trigger a re-layout / re-render.

Next steps

1. Trace the real event pipeline (process_event → fire_callbacks → on_click).
2. Verify the debug API synthesizes both mouse-down + mouse-up.
3. Test with a real mouse click (not via debug API) to isolate whether the bug is in the debug API or the real event flow.

Bug 12 – Titlebar should use block layout, not flex

Fix (optional, after Bug 7)

Change the container from display: flex to display: block. The title text can be centred via text-align: center (already present). The padding-left / padding-right already reserves button space. With display: block the text node would automatically fill the content box, and overflow: hidden + text-overflow: ellipsis would work correctly without needing flex-grow.

Summary – Fix order