IO: fix writing to incorrect union section for MouseSource in AddMousePosEvent and AddMouseButtonEvent. (#6727, #2702)

Technically may have had no side-effects unless non-standard alignment used.

docs/CHANGELOG.txt

@@ -54,6 +54,9 @@ Other changes:
   of individual ImDrawList's buffer sizes when a dimming/modal background is rendered. (#6716)
 - ImDrawList: Fixed OOB access in _CalcCircleAutoSegmentCount when passing excessively
   large radius to AddCircle(). (#6657, #5317) [@EggsyCRO, @jdpatdiscord]
+- IO: Fixed io.AddMousePosEvent() and io.AddMouseButtonEvent() writing MouseSource to
+  wrong union section. Was semantically incorrect and accidentally had no side-effects
+  with default compiler alignment settings. (#6727) [@RickHuang2001]
 - Misc: Made multiple calls to Render() during the same frame early out faster.
 - Debug Tools: Metrics: Fixed "Drawlists" section and per-viewport equivalent
   appearing empty (regression in 1.89.8).

imgui.cpp

@@ -1531,7 +1531,7 @@ void ImGuiIO::AddMousePosEvent(float x, float y)
     e.EventId = g.InputEventsNextEventId++;
     e.MousePos.PosX = pos.x;
     e.MousePos.PosY = pos.y;
-    e.MouseWheel.MouseSource = g.InputEventsNextMouseSource;
+    e.MousePos.MouseSource = g.InputEventsNextMouseSource;
     g.InputEventsQueue.push_back(e);
 }
 
@@ -1555,7 +1555,7 @@ void ImGuiIO::AddMouseButtonEvent(int mouse_button, bool down)
     e.EventId = g.InputEventsNextEventId++;
     e.MouseButton.Button = mouse_button;
     e.MouseButton.Down = down;
-    e.MouseWheel.MouseSource = g.InputEventsNextMouseSource;
+    e.MouseButton.MouseSource = g.InputEventsNextMouseSource;
     g.InputEventsQueue.push_back(e);
 }
 
@@ -8852,8 +8852,8 @@ static const char* GetMouseSourceName(ImGuiMouseSource source)
 static void DebugPrintInputEvent(const char* prefix, const ImGuiInputEvent* e)
 {
     ImGuiContext& g = *GImGui;
-    if (e->Type == ImGuiInputEventType_MousePos)    { if (e->MousePos.PosX == -FLT_MAX && e->MousePos.PosY == -FLT_MAX) IMGUI_DEBUG_LOG_IO("[io] %s: MousePos (-FLT_MAX, -FLT_MAX)\n", prefix); else IMGUI_DEBUG_LOG_IO("[io] %s: MousePos (%.1f, %.1f) (%s)\n", prefix, e->MousePos.PosX, e->MousePos.PosY, GetMouseSourceName(e->MouseWheel.MouseSource)); return; }
-    if (e->Type == ImGuiInputEventType_MouseButton) { IMGUI_DEBUG_LOG_IO("[io] %s: MouseButton %d %s (%s)\n", prefix, e->MouseButton.Button, e->MouseButton.Down ? "Down" : "Up", GetMouseSourceName(e->MouseWheel.MouseSource)); return; }
+    if (e->Type == ImGuiInputEventType_MousePos)    { if (e->MousePos.PosX == -FLT_MAX && e->MousePos.PosY == -FLT_MAX) IMGUI_DEBUG_LOG_IO("[io] %s: MousePos (-FLT_MAX, -FLT_MAX)\n", prefix); else IMGUI_DEBUG_LOG_IO("[io] %s: MousePos (%.1f, %.1f) (%s)\n", prefix, e->MousePos.PosX, e->MousePos.PosY, GetMouseSourceName(e->MousePos.MouseSource)); return; }
+    if (e->Type == ImGuiInputEventType_MouseButton) { IMGUI_DEBUG_LOG_IO("[io] %s: MouseButton %d %s (%s)\n", prefix, e->MouseButton.Button, e->MouseButton.Down ? "Down" : "Up", GetMouseSourceName(e->MouseButton.MouseSource)); return; }
     if (e->Type == ImGuiInputEventType_MouseWheel)  { IMGUI_DEBUG_LOG_IO("[io] %s: MouseWheel (%.3f, %.3f) (%s)\n", prefix, e->MouseWheel.WheelX, e->MouseWheel.WheelY, GetMouseSourceName(e->MouseWheel.MouseSource)); return; }
     if (e->Type == ImGuiInputEventType_Key)         { IMGUI_DEBUG_LOG_IO("[io] %s: Key \"%s\" %s\n", prefix, ImGui::GetKeyName(e->Key.Key), e->Key.Down ? "Down" : "Up"); return; }
     if (e->Type == ImGuiInputEventType_Text)        { IMGUI_DEBUG_LOG_IO("[io] %s: Text: %c (U+%08X)\n", prefix, e->Text.Char, e->Text.Char); return; }