RangeSelect/MultiSelect: Demo sharing selection helper code. Fixed static analyzer warnings.

imgui.h

@@ -2662,11 +2662,13 @@ struct ImColor
 #define IMGUI_HAS_MULTI_SELECT      // Multi-Select/Range-Select WIP branch // <-- This is currently _not_ in the top of imgui.h to prevent merge conflicts.
 
 // Flags for BeginMultiSelect().
-// This system is designed to allow mouse/keyboard multi-selection, including support for range-selection (SHIFT + click) which is difficult to re-implement manually.
-// If you disable multi-selection with ImGuiMultiSelectFlags_NoMultiSelect (which is provided for consistency and flexibility), the whole BeginMultiSelect() system
-// becomes largely overkill as you can handle single-selection in a simpler manner by just calling Selectable() and reacting on clicks yourself.
+// This system is designed to allow mouse/keyboard multi-selection, including support for range-selection (SHIFT + click),
+// which is difficult to re-implement manually. If you disable multi-selection with ImGuiMultiSelectFlags_NoMultiSelect
+// (which is provided for consistency and flexibility), the whole BeginMultiSelect() system becomes largely overkill as
+// 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

imgui_demo.cpp

@@ -2739,6 +2739,38 @@ static void ShowDemoWindowWidgets()
     }
 }
 
+// [Advanced] Helper class to simulate storage of a multi-selection state, used by the advanced multi-selection demos.
+// We use ImGuiStorage (simple key->value storage) to avoid external dependencies but it's probably not optimal.
+// To store a single-selection:
+// - You only need a single variable and don't need any of this!
+// To store a multi-selection, in your real application you could:
+// - Use intrusively stored selection (e.g. 'bool IsSelected' inside your object). This is by far the simplest
+//   way to store your selection data, but it means you cannot have multiple simultaneous views over your objects.
+//   This is what may of the simpler demos in this file are using (so they are not using this class).
+// - Otherwise, any externally stored unordered_set/set/hash/map/interval trees (storing indices, objects id, etc.)
+//   are generally appropriate. Even a large array of bool might work for you...
+struct ExampleSelectionData
+{
+    ImGuiStorage                        Storage;
+    int                                 SelectedCount;  // Number of selected items (storage will keep this updated)
+
+    ExampleSelectionData()              { Clear(); }
+    void Clear()                        { Storage.Clear(); SelectedCount = 0; }
+    bool GetSelected(int id) const      { return Storage.GetInt((ImGuiID)id) != 0; }
+    void SetSelected(int id, bool v)    { int* p_int = Storage.GetIntRef((ImGuiID)id); if (*p_int == (int)v) return; SelectedCount = v ? (SelectedCount + 1) : (SelectedCount - 1); *p_int = (bool)v; }
+    int  GetSelectedCount() const       { return SelectedCount; }
+
+    // When using SelectAll() / SetRange() we assume that our objects ID are indices.
+    // In this demo we always store selection using indices and never in another manner (e.g. object ID or pointers).
+    // If your selection system is storing selection using object ID and you want to support Shift+Click range-selection,
+    // you will need a way to iterate from one object to another given the ID you use.
+    // You are likely to need some kind of data structure to convert 'view index' from/to 'ID'.
+    // FIXME-MULTISELECT: Would be worth providing a demo of doing this.
+    // FIXME-MULTISELECT: SetRange() is currently very inefficient since it doesn't take advantage of the fact that ImGuiStorage stores sorted key.
+    void SetRange(int a, int b, bool v) { if (b < a) { int tmp = b; b = a; a = tmp; } for (int n = a; n <= b; n++) SetSelected(n, v); }
+    void SelectAll(int count)           { Storage.Data.resize(count); for (int n = 0; n < count; n++) Storage.Data[n] = ImGuiStoragePair((ImGuiID)n, 1); SelectedCount = count; } // This could be using SetRange() but this is faster.
+};
+
 static void ShowDemoWindowMultiSelect()
 {
     IMGUI_DEMO_MARKER("Widgets/Selection State");
@@ -2783,22 +2815,8 @@ static void ShowDemoWindowMultiSelect()
         if (ImGui::TreeNode("Multiple Selection (Full)"))
         {
             // Demonstrate holding/updating multi-selection data and using the BeginMultiSelect/EndMultiSelect API to support range-selection and clipping.
-            // In this demo we use ImGuiStorage (simple key->value storage) to avoid external dependencies but it's probably not optimal.
-            // In your real code you could use e.g std::unordered_set<> or your own data structure for storing selection.
-            // If you don't mind being limited to one view over your objects, the simplest way is to use an intrusive selection (e.g. store bool inside object, as used in examples above).
-            // Otherwise external set/hash/map/interval trees (storing indices, etc.) may be appropriate.
-            struct MySelection
-            {
-                ImGuiStorage Storage;
-                void Clear() { Storage.Clear(); }
-                void SelectAll(int count) { Storage.Data.reserve(count); Storage.Data.resize(0); for (int n = 0; n < count; n++) Storage.Data.push_back(ImGuiStoragePair((ImGuiID)n, 1)); }
-                void SetRange(int a, int b, int sel) { if (b < a) { int tmp = b; b = a; a = tmp; } for (int n = a; n <= b; n++) Storage.SetInt((ImGuiID)n, sel); }
-                bool GetSelected(int id) const { return Storage.GetInt((ImGuiID)id) != 0; }
-                void SetSelected(int id, bool v) { SetRange(id, id, v ? 1 : 0); }
-            };
-
             static int selection_ref = 0;   // Selection pivot (last clicked item, we need to preserve this to handle range-select)
-            static MySelection selection;
+            static ExampleSelectionData selection;
             const char* random_names[] =
             {
                 "Artichoke", "Arugula", "Asparagus", "Avocado", "Bamboo Shoots", "Bean Sprouts", "Beans", "Beet", "Belgian Endive", "Bell Pepper",
@@ -2812,8 +2830,8 @@ static void ShowDemoWindowMultiSelect()
 
             if (ImGui::BeginListBox("##Basket", ImVec2(-FLT_MIN, ImGui::GetFontSize() * 20)))
             {
-                ImGuiMultiSelectData* multi_select_data = ImGui::BeginMultiSelect(0, (void*)(intptr_t)selection_ref, selection.GetSelected((int)selection_ref));
-                if (multi_select_data->RequestClear) { selection.Clear(); }
+                ImGuiMultiSelectData* multi_select_data = ImGui::BeginMultiSelect(ImGuiMultiSelectFlags_None, (void*)(intptr_t)selection_ref, selection.GetSelected((int)selection_ref));
+                if (multi_select_data->RequestClear)     { selection.Clear(); }
                 if (multi_select_data->RequestSelectAll) { selection.SelectAll(COUNT); }
                 ImGuiListClipper clipper;
                 clipper.Begin(COUNT);
@@ -2836,9 +2854,9 @@ static void ShowDemoWindowMultiSelect()
                 multi_select_data = ImGui::EndMultiSelect();
                 selection_ref = (int)(intptr_t)multi_select_data->RangeSrc;
                 ImGui::EndListBox();
-                if (multi_select_data->RequestClear) { selection.Clear(); }
+                if (multi_select_data->RequestClear)     { selection.Clear(); }
                 if (multi_select_data->RequestSelectAll) { selection.SelectAll(COUNT); }
-                if (multi_select_data->RequestSetRange) { selection.SetRange((int)(intptr_t)multi_select_data->RangeSrc, (int)(intptr_t)multi_select_data->RangeDst, multi_select_data->RangeValue ? 1 : 0); }
+                if (multi_select_data->RequestSetRange)  { selection.SetRange((int)(intptr_t)multi_select_data->RangeSrc, (int)(intptr_t)multi_select_data->RangeDst, multi_select_data->RangeValue ? 1 : 0); }
             }
             ImGui::TreePop();
         }

imgui_widgets.cpp

@@ -7131,10 +7131,10 @@ void ImGui::MultiSelectItemFooter(ImGuiID id, bool* p_selected, bool* p_pressed)
     // Auto-select as you navigate a list
     if (g.NavJustMovedToId == id)
     {
-        if (!g.IO.KeyCtrl)
-            selected = pressed = true;
-        else if (g.IO.KeyCtrl && g.IO.KeyShift)
+        if (is_ctrl && is_shift)
             pressed = true;
+        else if (!is_ctrl)
+            selected = pressed = true;
     }
 
     // Right-click handling: this could be moved at the Selectable() level.
@@ -7203,9 +7203,9 @@ void ImGui::MultiSelectItemFooter(ImGuiID id, bool* p_selected, bool* p_pressed)
         }
         else if (input_source == ImGuiInputSource_Keyboard || input_source == ImGuiInputSource_Gamepad)
         {
-            if (!is_multiselect)
+            if (is_multiselect && is_shift && !is_ctrl)
                 ms->Out.RequestClear = true;
-            else if (is_shift && !is_ctrl && is_multiselect)
+            else if (!is_multiselect)
                 ms->Out.RequestClear = true;
         }
     }