Add SetWindowHitTest/SetNextWindowHitTest pair to allow clicking trou…

…gh windows.

imgui.cpp

@@ -803,6 +803,7 @@ static const float WINDOWS_MOUSE_WHEEL_SCROLL_LOCK_TIMER    = 2.00f;    // Lock
 //-------------------------------------------------------------------------
 
 static void             SetCurrentWindow(ImGuiWindow* window);
+static void             SetWindowHitTest(ImGuiWindow* window, ImGuiHitTestData hitTest);
 static void             FindHoveredWindow();
 static ImGuiWindow*     CreateNewWindow(const char* name, ImGuiWindowFlags flags);
 static ImVec2           CalcNextScrollFromScrollTargetAndClamp(ImGuiWindow* window, bool snap_on_edges);
@@ -2760,6 +2761,7 @@ ImGuiWindow::ImGuiWindow(ImGuiContext* context, const char* name)
     HiddenFramesCanSkipItems = HiddenFramesCannotSkipItems = 0;
     SetWindowPosAllowFlags = SetWindowSizeAllowFlags = SetWindowCollapsedAllowFlags = ImGuiCond_Always | ImGuiCond_Once | ImGuiCond_FirstUseEver | ImGuiCond_Appearing;
     SetWindowPosVal = SetWindowPosPivot = ImVec2(FLT_MAX, FLT_MAX);
+    WindowHitTest = ImGuiHitTestData();
 
     InnerRect = ImRect(0.0f, 0.0f, 0.0f, 0.0f); // Clear so the InnerRect.GetSize() code in Begin() doesn't lead to overflow even if the result isn't used.
 
@@ -4295,6 +4297,9 @@ static void FindHoveredWindow()
         if (!bb.Contains(g.IO.MousePos))
             continue;
 
+        if (window->WindowHitTest.Callback && !window->WindowHitTest.Callback(g.IO.MousePos, window->Pos, window->Size, window->WindowHitTest.UserData))
+            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;
@@ -4323,6 +4328,7 @@ bool ImGui::IsMouseHoveringRect(const ImVec2& r_min, const ImVec2& r_max, bool c
     const ImRect rect_for_touch(rect_clipped.Min - g.Style.TouchExtraPadding, rect_clipped.Max + g.Style.TouchExtraPadding);
     bool result = rect_for_touch.Contains(g.IO.MousePos);
 
+    ImGuiWindow* window = g.CurrentWindow;
     if (result && window->DC.HitTest.Callback)
         return window->DC.HitTest.Callback(g.IO.MousePos, r_min, r_max, window->DC.HitTest.UserData);
     else
@@ -5509,6 +5515,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         window->ContentSizeExplicit = ImVec2(0.0f, 0.0f);
     if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasCollapsed)
         SetWindowCollapsed(window, g.NextWindowData.CollapsedVal, g.NextWindowData.CollapsedCond);
+    if (g.NextWindowData.WindowHitTest)
+        SetWindowHitTest(window, g.NextWindowData.WindowHitTestVal);
     if (g.NextWindowData.Flags & ImGuiNextWindowDataFlags_HasFocus)
         FocusWindow(window);
     if (window->Appearing)
@@ -6489,6 +6497,17 @@ void ImGui::SetWindowFocus(const char* name)
     }
 }
 
+static void SetWindowHitTest(ImGuiWindow* window, ImGuiHitTestData hitTest)
+{
+    window->WindowHitTest = hitTest;
+}
+
+void ImGui::SetWindowHitTest(const char* name, ImGuiHitTestCallback callback, void* user_data)
+{
+    if (ImGuiWindow* window = FindWindowByName(name))
+        SetWindowHitTest(window, ImGuiHitTestData(callback, user_data));
+}
+
 void ImGui::SetNextWindowPos(const ImVec2& pos, ImGuiCond cond, const ImVec2& pivot)
 {
     ImGuiContext& g = *GImGui;
@@ -6555,6 +6574,13 @@ void ImGui::SetNextWindowBgAlpha(float alpha)
     g.NextWindowData.BgAlphaVal = alpha;
 }
 
+void ImGui::SetNextWindowHitTest(ImGuiHitTestCallback callback, void* user_data)
+{
+    ImGuiContext& g = *GImGui;
+    g.NextWindowData.WindowHitTest = true;
+    g.NextWindowData.WindowHitTestVal = ImGuiHitTestData(callback, user_data);
+}
+
 ImDrawList* ImGui::GetWindowDrawList()
 {
     ImGuiWindow* window = GetCurrentWindow();

imgui.h

@@ -313,6 +313,7 @@ namespace ImGui
     IMGUI_API void          SetNextWindowCollapsed(bool collapsed, ImGuiCond cond = 0);                 // set next window collapsed state. call before Begin()
     IMGUI_API void          SetNextWindowFocus();                                                       // set next window to be focused / top-most. call before Begin()
     IMGUI_API void          SetNextWindowBgAlpha(float alpha);                                          // set next window background color alpha. helper to easily override the Alpha component of ImGuiCol_WindowBg/ChildBg/PopupBg. you may also use ImGuiWindowFlags_NoBackground.
+    IMGUI_API void          SetNextWindowHitTest(ImGuiHitTestCallback callback, void* user_data = NULL);
     IMGUI_API void          SetWindowPos(const ImVec2& pos, ImGuiCond cond = 0);                        // (not recommended) set current window position - call within Begin()/End(). prefer using SetNextWindowPos(), as this may incur tearing and side-effects.
     IMGUI_API void          SetWindowSize(const ImVec2& size, ImGuiCond cond = 0);                      // (not recommended) set current window size - call within Begin()/End(). set to ImVec2(0, 0) to force an auto-fit. prefer using SetNextWindowSize(), as this may incur tearing and minor side-effects.
     IMGUI_API void          SetWindowCollapsed(bool collapsed, ImGuiCond cond = 0);                     // (not recommended) set current window collapsed state. prefer using SetNextWindowCollapsed().
@@ -322,6 +323,7 @@ namespace ImGui
     IMGUI_API void          SetWindowSize(const char* name, const ImVec2& size, ImGuiCond cond = 0);    // set named window size. set axis to 0.0f to force an auto-fit on this axis.
     IMGUI_API void          SetWindowCollapsed(const char* name, bool collapsed, ImGuiCond cond = 0);   // set named window collapsed state
     IMGUI_API void          SetWindowFocus(const char* name);                                           // set named window to be focused / top-most. use NULL to remove focus.
+    IMGUI_API void          SetWindowHitTest(const char* name, ImGuiHitTestCallback callback, void* user_data = NULL);
 
     // Content region
     // - Those functions are bound to be redesigned soon (they are confusing, incomplete and return values in local window coordinates which increases confusion)

imgui_internal.h

@@ -938,6 +938,7 @@ struct ImGuiNextWindowData
     ImGuiCond                   PosCond;
     ImGuiCond                   SizeCond;
     ImGuiCond                   CollapsedCond;
+    bool                        WindowHitTest;
     ImVec2                      PosVal;
     ImVec2                      PosPivotVal;
     ImVec2                      SizeVal;
@@ -949,6 +950,7 @@ struct ImGuiNextWindowData
     void*                       SizeCallbackUserData;
     float                       BgAlphaVal;             // Override background alpha
     ImVec2                      MenuBarOffsetMinVal;    // *Always on* This is not exposed publicly, so we don't clear it.
+    ImGuiHitTestData            WindowHitTestVal;
 
     ImGuiNextWindowData()       { memset(this, 0, sizeof(*this)); }
     inline void ClearFlags()    { Flags = ImGuiNextWindowDataFlags_None; }
@@ -1617,6 +1619,7 @@ struct IMGUI_API ImGuiWindow
     ImGuiCond               SetWindowCollapsedAllowFlags;       // store acceptable condition flags for SetNextWindowCollapsed() use.
     ImVec2                  SetWindowPosVal;                    // store window position when using a non-zero Pivot (position set needs to be processed when we know the window size)
     ImVec2                  SetWindowPosPivot;                  // store window pivot for positioning. ImVec2(0, 0) when positioning from top-left corner; ImVec2(0.5f, 0.5f) for centering; ImVec2(1, 1) for bottom right.
+    ImGuiHitTestData        WindowHitTest;
 
     ImVector<ImGuiID>       IDStack;                            // ID stack. ID are hashes seeded with the value at the top of the stack. (In theory this should be in the TempData structure)
     ImGuiWindowTempData     DC;                                 // Temporary per-window data, reset at the beginning of the frame. This used to be called ImGuiDrawContext, hence the "DC" variable name.