borderless_movable: handle absolute or relative mouse position

pthom · Jan 3, 2024 · 8448f4b · 8448f4b
1 parent ba7570d
commit 8448f4b
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Showing 4 changed files with 40 additions and 23 deletions.
diff --git a/src/hello_imgui/internal/backend_impls/abstract_runner.cpp b/src/hello_imgui/internal/backend_impls/abstract_runner.cpp
@@ -509,13 +509,7 @@ void AbstractRunner::RenderGui()
     if (params.appWindowParams.borderless) // Need to add params.appWindowParams.borderlessResizable
     {
 #if !defined(HELLOIMGUI_MOBILEDEVICE) && !defined(__EMSCRIPTEN__)
-        bool shouldClose = HandleBorderlessMovable(mWindow,
-                                mBackendWindowHelper.get(),
-                                params.appWindowParams.borderlessMovable,
-                                params.appWindowParams.borderlessResizable,
-                                params.appWindowParams.borderlessClosable,
-                                params.appWindowParams.borderlessHighlightColor
-        );
+        bool shouldClose = HandleBorderlessMovable(mWindow, mBackendWindowHelper.get(), params);
         if (shouldClose)
             params.appShallExit = true;
 #endif

diff --git a/src/hello_imgui/internal/borderless_movable.cpp b/src/hello_imgui/internal/borderless_movable.cpp
@@ -9,13 +9,23 @@ namespace HelloImGui
     bool HandleBorderlessMovable(
         BackendApi::WindowPointer window,
         BackendApi::IBackendWindowHelper * backendWindowHelper,
-        bool borderlessMovable,
-        bool borderlessResizable,
-        bool borderlessClosable,
-        ImVec4 borderlessHighlightColor)
+        const HelloImGui::RunnerParams& runnerParams
+        )
     {
+        // - If using viewports, the mouse position is absolute, and we can confidently move the window
+        //   knowing that the mouse position will not be affected.
+        // - If not using viewports, the mouse position is relative to the window, and the window may
+        //   jump from position to position when dragged: MouseDelta is not reliable in this case
+        // => in this case, we do not move the window
+        bool isMousePositionAbsolute = ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_ViewportsEnable;
+
         bool shouldClose = false;
 
+        bool borderlessMovable = runnerParams.appWindowParams.borderlessMovable;
+        bool borderlessResizable = runnerParams.appWindowParams.borderlessResizable;
+        bool borderlessClosable = runnerParams.appWindowParams.borderlessClosable;
+        ImVec4 borderlessHighlightColor = runnerParams.appWindowParams.borderlessHighlightColor;
+
         ImU32 highlightColorU32 = ImGui::GetColorU32(borderlessHighlightColor);
         if (borderlessHighlightColor.w == 0.f)
             highlightColorU32 = ImGui::GetColorU32(ImGuiCol_TitleBg, 0.6f);
@@ -29,9 +39,13 @@ namespace HelloImGui
             // Update dragging state
             ImVec2 mousePos = ImGui::GetMousePos();
             static bool isDragging = false;
+
+            static ImVec2 mouseDragLastPos; // used to store DragDelta when isMousePositionAbsolute==false
+
             if (dragArea.Contains(mousePos) && !isDragging && ImGui::IsMouseDown(ImGuiMouseButton_Left))
             {
                 isDragging = true;
+                mouseDragLastPos = mousePos;
             }
             if (!ImGui::IsMouseDown(ImGuiMouseButton_Left) && isDragging)
                 isDragging = false;
@@ -49,13 +63,25 @@ namespace HelloImGui
             // Move window if dragging
             if (isDragging)
             {
-                ImVec2 dragDelta = ImGui::GetMouseDragDelta(0);
-                ImGui::ResetMouseDragDelta(0);
+                ImVec2 dragDelta;
+                if (isMousePositionAbsolute)
+                {
+                    dragDelta = ImGui::GetMouseDragDelta(0);
+                    ImGui::ResetMouseDragDelta(0);
+                    ImGui::ResetMouseDragDelta(ImGuiMouseButton_Left);
+                }
+                else
+                {
+                    dragDelta = mousePos - mouseDragLastPos;
+                    // take the window movement into account, since our future mouse position
+                    // will be relative to the moved window!
+                    mouseDragLastPos = mousePos - dragDelta;
+                }
+
                 auto windowBounds = backendWindowHelper->GetWindowBounds(window);
-                windowBounds.position[0] += (int)dragDelta.x;
-                windowBounds.position[1] += (int)dragDelta.y;
+                windowBounds.position[0] += (int)(dragDelta.x);
+                windowBounds.position[1] += (int)(dragDelta.y);
                 backendWindowHelper->SetWindowBounds(window, windowBounds);
-                ImGui::ResetMouseDragDelta(ImGuiMouseButton_Left);
             }
 
             // Set mouse cursor: probably not visible for moving (the cursor will be the classic arrow)
@@ -75,8 +101,8 @@ namespace HelloImGui
                 ImVec2 btnPos(topRight.x - btnSize.x, topRight.y);
                 ImRect btnArea(btnPos, btnPos + btnSize);
 
-                auto colorButton = ImGui::GetColorU32(ImGuiCol_Button, 0.95f);
-                colorButton = 0xFF0000BB;
+                //auto colorButton = ImGui::GetColorU32(ImGuiCol_Button, 0.95f);
+                ImU32 colorButton = 0xFF0000BB;
                 ImGui::GetForegroundDrawList()->AddCircleFilled(
                     btnArea.GetCenter(),
                     btnSize.x * 0.5f,

diff --git a/src/hello_imgui/internal/borderless_movable.h b/src/hello_imgui/internal/borderless_movable.h
@@ -9,9 +9,6 @@ namespace HelloImGui
     bool HandleBorderlessMovable(
         BackendApi::WindowPointer window,
         BackendApi::IBackendWindowHelper * backendWindowHelper,
-        bool borderlessMovable,
-        bool borderlessResizable,
-        bool borderlessClosable,
-        ImVec4 borderlessHighlightColor
+        const HelloImGui::RunnerParams& runnerParams
     );
 }
diff --git a/src/hello_imgui_demos/hello_imgui_demodocking/hello_imgui_demodocking.main.cpp b/src/hello_imgui_demos/hello_imgui_demodocking/hello_imgui_demodocking.main.cpp
@@ -668,7 +668,7 @@ int main(int, char**)
     // First, tell HelloImGui that we want full screen dock space (this will create "MainDockSpace")
     runnerParams.imGuiWindowParams.defaultImGuiWindowType = HelloImGui::DefaultImGuiWindowType::ProvideFullScreenDockSpace;
     // In this demo, we also demonstrate multiple viewports: you can drag windows outside out the main window in order to put their content into new native windows
-    runnerParams.imGuiWindowParams.enableViewports = true;
+    runnerParams.imGuiWindowParams.enableViewports = false;
     // Set the default layout
     runnerParams.dockingParams = CreateDefaultLayout(appState);
     // Add alternative layouts