Internals: backport window HitTestHole code from docking branch + RenderRectFilledWithHole() helper. (#1512, #3368)

imgui.cpp

@@ -4295,6 +4295,16 @@ static void FindHoveredWindow()
         if (!bb.Contains(g.IO.MousePos))
             continue;
 
+        // Support for one rectangular hole in any given window
+        // FIXME: Consider generalizing hit-testing override (with more generic data, callback, etc.) (#1512)
+        if (window->HitTestHoleSize.x != 0)
+        {
+            ImVec2 hole_pos(window->Pos.x + (float)window->HitTestHoleOffset.x, window->Pos.y + (float)window->HitTestHoleOffset.y);
+            ImVec2 hole_size((float)window->HitTestHoleSize.x, (float)window->HitTestHoleSize.y);
+            if (ImRect(hole_pos, hole_pos + hole_size).Contains(g.IO.MousePos))
+                continue;
+        }
+
         // Those seemingly unnecessary extra tests are because the code here is a little different in viewport/docking branches.
         if (hovered_window == NULL)
             hovered_window = window;
@@ -5940,6 +5950,9 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         if (!(flags & ImGuiWindowFlags_NoTitleBar))
             RenderWindowTitleBarContents(window, title_bar_rect, name, p_open);
 
+        // Clear hit test shape every frame
+        window->HitTestHoleSize.x = window->HitTestHoleSize.y = 0;
+
         // Pressing CTRL+C while holding on a window copy its content to the clipboard
         // This works but 1. doesn't handle multiple Begin/End pairs, 2. recursing into another Begin/End pair - so we need to work that out and add better logging scope.
         // Maybe we can support CTRL+C on every element?
@@ -6429,6 +6442,13 @@ void ImGui::SetWindowCollapsed(ImGuiWindow* window, bool collapsed, ImGuiCond co
     window->Collapsed = collapsed;
 }
 
+void ImGui::SetWindowHitTestHole(ImGuiWindow* window, const ImVec2& pos, const ImVec2& size)
+{
+    IM_ASSERT(window->HitTestHoleSize.x == 0);     // We don't support multiple holes/hit test filters
+    window->HitTestHoleSize = ImVec2ih(size);
+    window->HitTestHoleOffset = ImVec2ih(pos - window->Pos);
+}
+
 void ImGui::SetWindowCollapsed(bool collapsed, ImGuiCond cond)
 {
     SetWindowCollapsed(GImGui->CurrentWindow, collapsed, cond);

imgui_draw.cpp

@@ -3501,6 +3501,22 @@ void ImGui::RenderRectFilledRangeH(ImDrawList* draw_list, const ImRect& rect, Im
     draw_list->PathFillConvex(col);
 }
 
+void ImGui::RenderRectFilledWithHole(ImDrawList* draw_list, ImRect outer, ImRect inner, ImU32 col, float rounding)
+{
+    const bool fill_L = (inner.Min.x > outer.Min.x);
+    const bool fill_R = (inner.Max.x < outer.Max.x);
+    const bool fill_U = (inner.Min.y > outer.Min.y);
+    const bool fill_D = (inner.Max.y < outer.Max.y);
+    if (fill_L) draw_list->AddRectFilled(ImVec2(outer.Min.x, inner.Min.y), ImVec2(inner.Min.x, inner.Max.y), col, rounding, (fill_U ? 0 : ImDrawCornerFlags_TopLeft) | (fill_D ? 0 : ImDrawCornerFlags_BotLeft));
+    if (fill_R) draw_list->AddRectFilled(ImVec2(inner.Max.x, inner.Min.y), ImVec2(outer.Max.x, inner.Max.y), col, rounding, (fill_U ? 0 : ImDrawCornerFlags_TopRight) | (fill_D ? 0 : ImDrawCornerFlags_BotRight));
+    if (fill_U) draw_list->AddRectFilled(ImVec2(inner.Min.x, outer.Min.y), ImVec2(inner.Max.x, inner.Min.y), col, rounding, (fill_L ? 0 : ImDrawCornerFlags_TopLeft) | (fill_R ? 0 : ImDrawCornerFlags_TopRight));
+    if (fill_D) draw_list->AddRectFilled(ImVec2(inner.Min.x, inner.Max.y), ImVec2(inner.Max.x, outer.Max.y), col, rounding, (fill_L ? 0 : ImDrawCornerFlags_BotLeft) | (fill_R ? 0 : ImDrawCornerFlags_BotRight));
+    if (fill_L && fill_U) draw_list->AddRectFilled(ImVec2(outer.Min.x, outer.Min.y), ImVec2(inner.Min.x, inner.Min.y), col, rounding, ImDrawCornerFlags_TopLeft);
+    if (fill_R && fill_U) draw_list->AddRectFilled(ImVec2(inner.Max.x, outer.Min.y), ImVec2(outer.Max.x, inner.Min.y), col, rounding, ImDrawCornerFlags_TopRight);
+    if (fill_L && fill_D) draw_list->AddRectFilled(ImVec2(outer.Min.x, inner.Max.y), ImVec2(inner.Min.x, outer.Max.y), col, rounding, ImDrawCornerFlags_BotLeft);
+    if (fill_R && fill_D) draw_list->AddRectFilled(ImVec2(inner.Max.x, inner.Max.y), ImVec2(outer.Max.x, outer.Max.y), col, rounding, ImDrawCornerFlags_BotRight);
+}
+
 // Helper for ColorPicker4()
 // NB: This is rather brittle and will show artifact when rounding this enabled if rounded corners overlap multiple cells. Caller currently responsible for avoiding that.
 // Spent a non reasonable amount of time trying to getting this right for ColorButton with rounding+anti-aliasing+ImGuiColorEditFlags_HalfAlphaPreview flag + various grid sizes and offsets, and eventually gave up... probably more reasonable to disable rounding altogether.

imgui_internal.h

@@ -1615,6 +1615,8 @@ struct IMGUI_API ImGuiWindow
     ImRect                  WorkRect;                           // Cover the whole scrolling region, shrunk by WindowPadding*1.0f on each side. This is meant to replace ContentRegionRect over time (from 1.71+ onward).
     ImRect                  ClipRect;                           // Current clipping/scissoring rectangle, evolve as we are using PushClipRect(), etc. == DrawList->clip_rect_stack.back().
     ImRect                  ContentRegionRect;                  // FIXME: This is currently confusing/misleading. It is essentially WorkRect but not handling of scrolling. We currently rely on it as right/bottom aligned sizing operation need some size to rely on.
+    ImVec2ih                HitTestHoleSize;                    // Define an optional rectangular hole where mouse will pass-through the window.
+    ImVec2ih                HitTestHoleOffset;
 
     int                     LastFrameActive;                    // Last frame number the window was Active.
     float                   LastTimeActive;                     // Last timestamp the window was Active (using float as we don't need high precision there)
@@ -1775,6 +1777,7 @@ namespace ImGui
     IMGUI_API void          SetWindowPos(ImGuiWindow* window, const ImVec2& pos, ImGuiCond cond = 0);
     IMGUI_API void          SetWindowSize(ImGuiWindow* window, const ImVec2& size, ImGuiCond cond = 0);
     IMGUI_API void          SetWindowCollapsed(ImGuiWindow* window, bool collapsed, ImGuiCond cond = 0);
+    IMGUI_API void          SetWindowHitTestHole(ImGuiWindow* window, const ImVec2& pos, const ImVec2& size);
 
     // Windows: Display Order and Focus Order
     IMGUI_API void          FocusWindow(ImGuiWindow* window);
@@ -1943,6 +1946,7 @@ namespace ImGui
     IMGUI_API void          RenderMouseCursor(ImDrawList* draw_list, ImVec2 pos, float scale, ImGuiMouseCursor mouse_cursor, ImU32 col_fill, ImU32 col_border, ImU32 col_shadow);
     IMGUI_API void          RenderArrowPointingAt(ImDrawList* draw_list, ImVec2 pos, ImVec2 half_sz, ImGuiDir direction, ImU32 col);
     IMGUI_API void          RenderRectFilledRangeH(ImDrawList* draw_list, const ImRect& rect, ImU32 col, float x_start_norm, float x_end_norm, float rounding);
+    IMGUI_API void          RenderRectFilledWithHole(ImDrawList* draw_list, ImRect outer, ImRect inner, ImU32 col, float rounding);
 
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
     // [1.71: 2019/06/07: Updating prototypes of some of the internal functions. Leaving those for reference for a short while]