Internals: Added SplitterBehavior(). (#319)

imgui.cpp

@@ -10184,6 +10184,55 @@ void ImGui::VerticalSeparator()
         LogText(" |");
 }
 
+bool ImGui::SplitterBehavior(ImGuiID id, const ImRect& bb, ImGuiAxis axis, float* size1, float* size2, float min_size1, float min_size2, float hover_extend)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = g.CurrentWindow;
+
+    const ImGuiItemFlags item_flags_backup = window->DC.ItemFlags;
+#ifdef IMGUI_HAS_NAV
+    window->DC.ItemFlags |= ImGuiItemFlags_NoNav | ImGuiItemFlags_NoNavDefaultFocus;
+#endif
+    bool add = ItemAdd(bb, id);
+    window->DC.ItemFlags = item_flags_backup;
+    if (!add)
+        return false;
+
+    bool hovered, held;
+    ImRect bb_interact = bb;
+    bb_interact.Expand(axis == ImGuiAxis_Y ? ImVec2(0.0f, hover_extend) : ImVec2(hover_extend, 0.0f));
+    ButtonBehavior(bb_interact, id, &hovered, &held, ImGuiButtonFlags_FlattenChilds | ImGuiButtonFlags_AllowOverlapMode);
+    if (g.ActiveId != id)
+        SetItemAllowOverlap();
+
+    if (held || (g.HoveredId == id && g.HoveredIdPreviousFrame == id))
+        SetMouseCursor(axis == ImGuiAxis_Y ? ImGuiMouseCursor_ResizeNS : ImGuiMouseCursor_ResizeEW);
+
+    ImRect bb_render = bb;
+    if (held)
+    {
+        ImVec2 mouse_delta_2d = g.IO.MousePos - g.ActiveIdClickOffset - bb_interact.Min;
+        float mouse_delta = (axis == ImGuiAxis_Y) ? mouse_delta_2d.y : mouse_delta_2d.x;
+
+        // Minimum pane size
+        if (mouse_delta < min_size1 - *size1)
+            mouse_delta = min_size1 - *size1;
+        if (mouse_delta > *size2 - min_size2)
+            mouse_delta = *size2 - min_size2;
+
+        // Apply resize
+        *size1 += mouse_delta;
+        *size2 -= mouse_delta;
+        bb_render.Translate((axis == ImGuiAxis_X) ? ImVec2(mouse_delta, 0.0f) : ImVec2(0.0f, mouse_delta));
+    }
+
+    // Render
+    const ImU32 col = GetColorU32(held ? ImGuiCol_SeparatorActive : hovered ? ImGuiCol_SeparatorHovered : ImGuiCol_Separator);
+    RenderFrame(bb_render.Min, bb_render.Max, col, true, g.Style.FrameRounding);
+
+    return held;
+}
+
 void ImGui::Spacing()
 {
     ImGuiWindow* window = GetCurrentWindow();

imgui_internal.h

@@ -221,6 +221,13 @@ enum ImGuiLayoutType_
     ImGuiLayoutType_Horizontal
 };
 
+enum ImGuiAxis
+{
+    ImGuiAxis_None = -1,
+    ImGuiAxis_X = 0,
+    ImGuiAxis_Y = 1,
+};
+
 enum ImGuiPlotType
 {
     ImGuiPlotType_Lines,
@@ -807,6 +814,7 @@ namespace ImGui
 
     IMGUI_API void          Scrollbar(ImGuiLayoutType direction);
     IMGUI_API void          VerticalSeparator();        // Vertical separator, for menu bars (use current line height). not exposed because it is misleading what it doesn't have an effect on regular layout.
+    IMGUI_API bool          SplitterBehavior(ImGuiID id, const ImRect& bb, ImGuiAxis axis, float* size1, float* size2, float min_size1, float min_size2, float hover_extend = 0.0f);
 
     // FIXME-WIP: New Columns API
     IMGUI_API void          BeginColumns(const char* id, int count, ImGuiColumnsFlags flags = 0); // setup number of columns. use an identifier to distinguish multiple column sets. close with EndColumns().