Demo: Improved Selectable() examples. (#1528)

imgui.h

@@ -376,8 +376,8 @@ namespace ImGui
     IMGUI_API bool          CollapsingHeader(const char* label, bool* p_open, ImGuiTreeNodeFlags flags = 0); // when 'p_open' isn't NULL, display an additional small close button on upper right of the header
 
     // Widgets: Selectable / Lists
-    IMGUI_API bool          Selectable(const char* label, bool selected = false, ImGuiSelectableFlags flags = 0, const ImVec2& size = ImVec2(0,0));  // size.x==0.0: use remaining width, size.x>0.0: specify width. size.y==0.0: use label height, size.y>0.0: specify height
-    IMGUI_API bool          Selectable(const char* label, bool* p_selected, ImGuiSelectableFlags flags = 0, const ImVec2& size = ImVec2(0,0));
+    IMGUI_API bool          Selectable(const char* label, bool selected = false, ImGuiSelectableFlags flags = 0, const ImVec2& size = ImVec2(0,0));  // "bool selected" carry the selection state (read-only). Selectable() is clicked is returns true so you can modify your selection state. size.x==0.0: use remaining width, size.x>0.0: specify width. size.y==0.0: use label height, size.y>0.0: specify height
+    IMGUI_API bool          Selectable(const char* label, bool* p_selected, ImGuiSelectableFlags flags = 0, const ImVec2& size = ImVec2(0,0));       // "bool* p_selected" point to the selection state (read-write), as a convenient helper.
     IMGUI_API bool          ListBox(const char* label, int* current_item, const char* const items[], int items_count, int height_in_items = -1);
     IMGUI_API bool          ListBox(const char* label, int* current_item, bool (*items_getter)(void* data, int idx, const char** out_text), void* data, int items_count, int height_in_items = -1);
     IMGUI_API bool          ListBoxHeader(const char* label, const ImVec2& size = ImVec2(0,0));     // use if you want to reimplement ListBox() will custom data or interactions. make sure to call ListBoxFooter() afterwards.

imgui_demo.cpp

@@ -609,24 +609,58 @@ void ImGui::ShowDemoWindow(bool* p_open)
 
         if (ImGui::TreeNode("Selectables"))
         {
+            // Selectable() has 2 overloads:
+            // - The one taking "bool selected" as a read-only selection information. When Selectable() has been clicked is returns true and you can alter selection state accordingly.
+            // - The one taking "bool* p_selected" as a read-write selection information (convenient in some cases)
+            // The earlier is more flexible, as in real application your selection may be stored in a different manner (in flags within objects, as an external list, etc).
             if (ImGui::TreeNode("Basic"))
             {
-                static bool selected[4] = { false, true, false, false };
-                ImGui::Selectable("1. I am selectable", &selected[0]);
-                ImGui::Selectable("2. I am selectable", &selected[1]);
+                static bool selection[5] = { false, true, false, false, false };
+                ImGui::Selectable("1. I am selectable", &selection[0]);
+                ImGui::Selectable("2. I am selectable", &selection[1]);
                 ImGui::Text("3. I am not selectable");
-                ImGui::Selectable("4. I am selectable", &selected[2]);
-                if (ImGui::Selectable("5. I am double clickable", selected[3], ImGuiSelectableFlags_AllowDoubleClick))
+                ImGui::Selectable("4. I am selectable", &selection[3]);
+                if (ImGui::Selectable("5. I am double clickable", selection[4], ImGuiSelectableFlags_AllowDoubleClick))
                     if (ImGui::IsMouseDoubleClicked(0))
-                        selected[3] = !selected[3];
+                        selection[4] = !selection[4];
                 ImGui::TreePop();
             }
-            if (ImGui::TreeNode("Rendering more text into the same block"))
+            if (ImGui::TreeNode("Selection State: Single Selection"))
             {
+                static int selected = -1;
+                for (int n = 0; n < 5; n++)
+                {
+                    char buf[32];
+                    sprintf(buf, "Object %d", n);
+                    if (ImGui::Selectable(buf, selected == n)) 
+                        selected = n;
+                }
+                ImGui::TreePop();
+            }
+            if (ImGui::TreeNode("Selection State: Multiple Selection"))
+            {
+                ShowHelpMarker("Hold CTRL and click to select multiple items.");
+                static bool selection[5] = { false, false, false, false, false };
+                for (int n = 0; n < 5; n++)
+                {
+                    char buf[32];
+                    sprintf(buf, "Object %d", n);
+                    if (ImGui::Selectable(buf, selection[n]))
+                    {
+                        if (!ImGui::GetIO().KeyCtrl)    // Clear selection when CTRL is not held
+                            memset(selection, 0, sizeof(selection)); 
+                        selection[n] ^= 1;
+                    }
+                }
+                ImGui::TreePop();
+            }
+            if (ImGui::TreeNode("Rendering more text into the same line"))
+            {
+                // Using the Selectable() override that takes "bool* p_selected" parameter and toggle your booleans automatically.
                 static bool selected[3] = { false, false, false };
-                ImGui::Selectable("main.c", &selected[0]);    ImGui::SameLine(300); ImGui::Text(" 2,345 bytes");
+                ImGui::Selectable("main.c",    &selected[0]); ImGui::SameLine(300); ImGui::Text(" 2,345 bytes");
                 ImGui::Selectable("Hello.cpp", &selected[1]); ImGui::SameLine(300); ImGui::Text("12,345 bytes");
-                ImGui::Selectable("Hello.h", &selected[2]);   ImGui::SameLine(300); ImGui::Text(" 2,345 bytes");
+                ImGui::Selectable("Hello.h",   &selected[2]); ImGui::SameLine(300); ImGui::Text(" 2,345 bytes");
                 ImGui::TreePop();
             }
             if (ImGui::TreeNode("In columns"))