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fix(input): handle the first Alt+wheel while idle in the wait path

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Alt + mouse wheel adjusts the font scale, but it was only handled in the
poll loop that runs after the app wakes. When the app was idle it blocks
in a single timed wait, and that first wheel event went straight to
ImGui, scrolling the window instead of changing the scale until a later
event arrived.

- The Alt+wheel handling is pulled into a shared helper used by both the
  idle wait path and the poll loop, so the first event while idle is
  consumed and triggers a redraw.
- Behaviour is otherwise unchanged: the visual scale updates smoothly and
  the font atlas is rebuilt once scrolling stops.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
DanS
2026-10-13 18:16:50 -05:00
co-authored by Claude Opus 4.8
parent fa1ba97286
commit 100d76b88f
1 changed files with 23 additions and 22 deletions
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src/main.cpp
+23 -22
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@@ -1639,6 +1639,25 @@ int main(int argc, char* argv[])
else if (isWindowStateEvent(e.type)) settleFrames = kSettleFrames;
};
// Deferred font-scale commit: smooth visual update during Alt+scroll,
// atlas rebuild after scrolling stops (~200ms idle).
Uint64 fontScaleCommitTick = 0; // 0 = nothing pending
// Alt + scroll wheel -> font scale. Returns true if the event was consumed.
auto handleAltWheel = [&](const SDL_Event& e) -> bool {
if (e.type != SDL_EVENT_MOUSE_WHEEL) return false;
if (!(SDL_GetModState() & SDL_KMOD_ALT)) return false;
float step = 0.05f * e.wheel.y;
float cur = dragonx::ui::Layout::userFontScale();
float next = std::max(1.0f, std::min(1.5f, cur + step));
if (next != cur) {
// Smooth preview — no atlas rebuild yet
dragonx::ui::Layout::setUserFontScaleVisual(next);
// Schedule atlas rebuild after scrolling stops
fontScaleCommitTick = SDL_GetTicks() + 200;
}
return true;
};
// Headless verification hook (DRAGONX_FULL_SWEEP=1, handled after present), hoisted so the pacing
// decision can keep its warm-up frames coming.
#if DRAGONX_ENABLE_UI_SWEEP
@@ -1726,7 +1745,8 @@ int main(int argc, char* argv[])
SDL_Event waitEvent;
if (waitMs > 0 && SDL_WaitEventTimeout(&waitEvent, waitMs)) {
noteEvent(waitEvent);
ImGui_ImplSDL3_ProcessEvent(&waitEvent);
if (handleAltWheel(waitEvent)) needsRedraw = true;
else ImGui_ImplSDL3_ProcessEvent(&waitEvent);
if (waitEvent.type == SDL_EVENT_QUIT) {
app.beginShutdown();
}
@@ -1828,29 +1848,10 @@ int main(int argc, char* argv[])
// Poll remaining events
SDL_Event event;
// Deferred font-scale commit: smooth visual update during Alt+scroll,
// atlas rebuild after scrolling stops (~200ms idle).
static Uint64 fontScaleCommitTick = 0; // 0 = nothing pending
while (SDL_PollEvent(&event)) {
noteEvent(event);
// Alt + scroll wheel: smooth font scale adjustment
if (event.type == SDL_EVENT_MOUSE_WHEEL) {
SDL_Keymod mods = SDL_GetModState();
if (mods & SDL_KMOD_ALT) {
float step = 0.05f * event.wheel.y;
float cur = dragonx::ui::Layout::userFontScale();
float next = std::max(1.0f, std::min(1.5f, cur + step));
if (next != cur) {
// Smooth preview — no atlas rebuild yet
dragonx::ui::Layout::setUserFontScaleVisual(next);
// Schedule atlas rebuild after scrolling stops
fontScaleCommitTick = SDL_GetTicks() + 200;
}
// Don't pass Alt+scroll to ImGui (would scroll windows)
continue;
}
}
// Alt + scroll wheel: smooth font scale adjustment (don't pass to ImGui: would scroll windows)
if (handleAltWheel(event)) continue;
ImGui_ImplSDL3_ProcessEvent(&event);
if (event.type == SDL_EVENT_QUIT) {