MultiSelect: Added ImGuiMultiSelectFlags_ClearOnClickWindowVoid. + Demo: showcase multiple selection scopes in same window.

imgui.h

@@ -2731,11 +2731,13 @@ struct ImColor
 // you can handle single-selection in a simpler manner by just calling Selectable() and reacting on clicks yourself.
 enum ImGuiMultiSelectFlags_
 {
-    ImGuiMultiSelectFlags_None              = 0,
-    ImGuiMultiSelectFlags_NoMultiSelect     = 1 << 0,
-    ImGuiMultiSelectFlags_NoUnselect        = 1 << 1,   // Disable unselecting items with CTRL+Click, CTRL+Space etc.
-    ImGuiMultiSelectFlags_NoSelectAll       = 1 << 2,   // Disable CTRL+A shortcut to set RequestSelectAll
-    ImGuiMultiSelectFlags_ClearOnEscape     = 1 << 3,   // Enable ESC shortcut to clear selection
+    ImGuiMultiSelectFlags_None                  = 0,
+    ImGuiMultiSelectFlags_NoMultiSelect         = 1 << 0,
+    ImGuiMultiSelectFlags_NoUnselect            = 1 << 1,   // Disable unselecting items with CTRL+Click, CTRL+Space etc.
+    ImGuiMultiSelectFlags_NoSelectAll           = 1 << 2,   // Disable CTRL+A shortcut to set RequestSelectAll
+    ImGuiMultiSelectFlags_ClearOnClickWindowVoid= 1 << 3,   // Clear selection when clicking on empty location within host window (use if BeginMultiSelect() covers a whole window)
+    //ImGuiMultiSelectFlags_ClearOnClickRectVoid= 1 << 4,   // Clear selection when clicking on empty location within rectangle covered by selection scope (use if multiple BeginMultiSelect() are used in the same host window)
+    ImGuiMultiSelectFlags_ClearOnEscape         = 1 << 5,   // Clear selection when pressing Escape while scope is focused.
 };
 
 // Abstract:

imgui_demo.cpp

@@ -2900,42 +2900,64 @@ static void ShowDemoWindowMultiSelect()
         // - Showcase clipping.
         // - Showcase basic drag and drop.
         // - Showcase TreeNode variant (note that tree node don't expand in the demo: supporting expanding tree nodes + clipping a separate thing).
+        // - Showcase having multiple multi-selection scopes in the same window.
         // - Showcase using inside a table.
         IMGUI_DEMO_MARKER("Widgets/Selection State/Multiple Selection (full, advanced)");
         ImGui::SetNextItemOpen(true, ImGuiCond_Once);
         if (ImGui::TreeNode("Multiple Selection (full, advanced)"))
         {
-            // Demonstrate holding/updating multi-selection data and using the BeginMultiSelect/EndMultiSelect API to support range-selection and clipping.
-            static ExampleSelection selections_data[1];
-            ExampleSelection* selection = &selections_data[0];
-
             // Options
             enum WidgetType { WidgetType_Selectable, WidgetType_TreeNode };
             static bool use_table = false;
             static bool use_drag_drop = true;
+            static bool multiple_selection_scopes = false;
             static WidgetType widget_type = WidgetType_TreeNode;
             if (ImGui::RadioButton("Selectables", widget_type == WidgetType_Selectable)) { widget_type = WidgetType_Selectable; }
             ImGui::SameLine();
             if (ImGui::RadioButton("Tree nodes", widget_type == WidgetType_TreeNode)) { widget_type = WidgetType_TreeNode; }
             ImGui::Checkbox("Use table", &use_table);
             ImGui::Checkbox("Use drag & drop", &use_drag_drop);
+            ImGui::Checkbox("Distinct selection scopes in same window", &multiple_selection_scopes);
 
-            // (spare brace to add a loop here later)
+            // When 'multiple_selection_scopes' is set we show 3 selection scopes in the host window instead of 1 in a scrolling window.
+            static ExampleSelection selections_data[3];
+            const int selection_scope_count = multiple_selection_scopes ? 3 : 1;
+            for (int selection_scope_n = 0; selection_scope_n < selection_scope_count; selection_scope_n++)
             {
-                ImGui::Text("Selection size: %d", selection->GetSelectionSize());
+                ExampleSelection* selection = &selections_data[selection_scope_n];
+
+                const int ITEMS_COUNT = multiple_selection_scopes ? 12 : 1000;
+                ImGui::PushID(selection_scope_n);
 
                 // Open a scrolling region
-                const int ITEMS_COUNT = 1000;
-                if (ImGui::BeginListBox("##Basket", ImVec2(-FLT_MIN, ImGui::GetFontSize() * 20)))
+                bool draw_selection = true;
+                if (multiple_selection_scopes)
+                {
+                    ImGui::SeparatorText("Selection scope");
+                }
+                else
+                {
+                    ImGui::Text("Selection size: %d", selection->GetSelectionSize());
+                    draw_selection = ImGui::BeginListBox("##Basket", ImVec2(-FLT_MIN, ImGui::GetFontSize() * 20));
+                }
+                if (draw_selection)
                 {
                     ImVec2 color_button_sz(ImGui::GetFontSize(), ImGui::GetFontSize());
                     if (widget_type == WidgetType_TreeNode)
                         ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(ImGui::GetStyle().ItemSpacing.x, 0.0f));
 
-                    ImGuiMultiSelectData* multi_select_data = ImGui::BeginMultiSelect(ImGuiMultiSelectFlags_None, (void*)(intptr_t)selection->RangeRef, selection->GetSelected(selection->RangeRef));
+                    ImGuiMultiSelectFlags flags = ImGuiMultiSelectFlags_None;
+                    if (multiple_selection_scopes)
+                        ;// flags |= ImGuiMultiSelectFlags_ClearOnClickRectVoid;
+                    else
+                        flags |= ImGuiMultiSelectFlags_ClearOnClickWindowVoid;
+                    ImGuiMultiSelectData* multi_select_data = ImGui::BeginMultiSelect(flags, (void*)(intptr_t)selection->RangeRef, selection->GetSelected(selection->RangeRef));
                     if (multi_select_data->RequestClear)     { selection->Clear(); }
                     if (multi_select_data->RequestSelectAll) { selection->SelectAll(ITEMS_COUNT); }
 
+                    if (multiple_selection_scopes)
+                        ImGui::Text("Selection size: %d", selection->GetSelectionSize());   // Draw counter below Separator and after BeginMultiSelect()
+
                     if (use_table)
                     {
                         ImGui::PushStyleVar(ImGuiStyleVar_CellPadding, ImVec2(0.0f, 0.0f));
@@ -3037,15 +3059,12 @@ static void ShowDemoWindowMultiSelect()
                     if (widget_type == WidgetType_TreeNode)
                         ImGui::PopStyleVar();
 
-                    ImGui::EndListBox();
+                    if (multiple_selection_scopes == false)
+                        ImGui::EndListBox();
                 }
+                ImGui::PopID(); // ImGui::PushID(selection_scope_n);
+            } // for each selection scope (1 or 3)
 
-                if (use_table)
-                {
-                    ImGui::EndTable();
-                    ImGui::PopStyleVar();
-                }
-            }
             ImGui::TreePop();
         }
         ImGui::TreePop();

imgui_internal.h

@@ -1720,6 +1720,7 @@ struct IMGUI_API ImGuiMultiSelectState
     ImGuiMultiSelectData    Out;                    // The Out requests are finalized and returned by EndMultiSelect()
     bool                    InRangeDstPassedBy;     // (Internal) set by the the item that match NavJustMovedToId when InRequestRangeSetNav is set.
     bool                    InRequestSetRangeNav;   // (Internal) set by BeginMultiSelect() when using Shift+Navigation. Because scrolling may be affected we can't afford a frame of lag with Shift+Navigation.
+    //ImRect                Rect;                   // Extent of selection scope between BeginMultiSelect() / EndMultiSelect(), used by ImGuiMultiSelectFlags_ClearOnClickRectVoid.
 
     ImGuiMultiSelectState() { Clear(); }
     void Clear()            { FocusScopeId = 0; In.Clear(); Out.Clear(); InRangeDstPassedBy = InRequestSetRangeNav = false; }

imgui_widgets.cpp

@@ -7188,6 +7188,17 @@ ImGuiMultiSelectData* ImGui::EndMultiSelect()
     ImGuiMultiSelectState* ms = &g.MultiSelectState;
     IM_ASSERT(g.MultiSelectState.FocusScopeId == g.CurrentFocusScopeId);
 
+    // Clear selection when clicking void?
+    // We specifically test for IsMouseDragPastThreshold(0) == false to allow box-selection!
+    if (g.MultiSelectFlags & ImGuiMultiSelectFlags_ClearOnClickWindowVoid)
+        if (IsWindowHovered() && g.HoveredId == 0)
+            if (IsMouseReleased(0) && IsMouseDragPastThreshold(0) == false && g.IO.KeyMods == ImGuiMod_None)
+            {
+                ms->Out.RequestClear = true;
+                ms->Out.RequestSelectAll = ms->Out.RequestSetRange = false;
+            }
+
+    // Unwind
     if (g.MultiSelectFlags & ImGuiMultiSelectFlags_NoUnselect)
         ms->Out.RangeValue = true;
     g.MultiSelectState.FocusScopeId = 0;