Demo: better showcase use of SetNextItemAllowOverlap(). (#6574, #6512, #3909, #517)

+ Merge some shallow changes from range-select branch.

docs/CHANGELOG.txt

@@ -38,6 +38,8 @@ Breaking changes:
 
 Other changes:
 
+- Demo: Better showcase use of SetNextItemAllowOverlap(). (#6574, #6512, #3909, #517)
+
 
 -----------------------------------------------------------------------
  VERSION 1.89.7 (Released 2023-07-04)

imgui_demo.cpp

@@ -1262,16 +1262,16 @@ static void ShowDemoWindowWidgets()
         IMGUI_DEMO_MARKER("Widgets/Selectables/Basic");
         if (ImGui::TreeNode("Basic"))
         {
-            static bool selection[5] = { false, true, false, false, false };
+            static bool selection[5] = { false, true, false, false };
             ImGui::Selectable("1. I am selectable", &selection[0]);
             ImGui::Selectable("2. I am selectable", &selection[1]);
-            ImGui::Text("(I am not selectable)");
-            ImGui::Selectable("4. I am selectable", &selection[3]);
-            if (ImGui::Selectable("5. I am double clickable", selection[4], ImGuiSelectableFlags_AllowDoubleClick))
+            ImGui::Selectable("3. I am selectable", &selection[2]);
+            if (ImGui::Selectable("4. I am double clickable", selection[3], ImGuiSelectableFlags_AllowDoubleClick))
                 if (ImGui::IsMouseDoubleClicked(0))
-                    selection[4] = !selection[4];
+                    selection[3] = !selection[3];
             ImGui::TreePop();
         }
+
         IMGUI_DEMO_MARKER("Widgets/Selectables/Single Selection");
         if (ImGui::TreeNode("Selection State: Single Selection"))
         {
@@ -1303,17 +1303,18 @@ static void ShowDemoWindowWidgets()
             }
             ImGui::TreePop();
         }
-        IMGUI_DEMO_MARKER("Widgets/Selectables/Rendering more text into the same line");
-        if (ImGui::TreeNode("Rendering more text into the same line"))
+        IMGUI_DEMO_MARKER("Widgets/Selectables/Rendering more items on the same line");
+        if (ImGui::TreeNode("Rendering more items on the same line"))
         {
-            // Using the Selectable() override that takes "bool* p_selected" parameter,
-            // this function toggle your bool value automatically.
+            // (1) Using SetNextItemAllowOverlap()
+            // (2) Using the Selectable() override that takes "bool* p_selected" parameter, the bool value is toggled automatically.
             static bool selected[3] = { false, false, false };
-            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::SetNextItemAllowOverlap(); ImGui::Selectable("main.c",    &selected[0]); ImGui::SameLine(); ImGui::SmallButton("Link 1");
+            ImGui::SetNextItemAllowOverlap(); ImGui::Selectable("Hello.cpp", &selected[1]); ImGui::SameLine(); ImGui::SmallButton("Link 2");
+            ImGui::SetNextItemAllowOverlap(); ImGui::Selectable("Hello.h",   &selected[2]); ImGui::SameLine(); ImGui::SmallButton("Link 3");
             ImGui::TreePop();
         }
+
         IMGUI_DEMO_MARKER("Widgets/Selectables/In columns");
         if (ImGui::TreeNode("In columns"))
         {
@@ -1349,6 +1350,7 @@ static void ShowDemoWindowWidgets()
             }
             ImGui::TreePop();
         }
+
         IMGUI_DEMO_MARKER("Widgets/Selectables/Grid");
         if (ImGui::TreeNode("Grid"))
         {
@@ -2795,11 +2797,11 @@ static void ShowDemoWindowLayout()
         // Text
         IMGUI_DEMO_MARKER("Layout/Basic Horizontal Layout/SameLine");
         ImGui::Text("Two items: Hello"); ImGui::SameLine();
-        ImGui::TextColored(ImVec4(1,1,0,1), "Sailor");
+        ImGui::TextColored(ImVec4(1, 1, 0, 1), "Sailor");
 
         // Adjust spacing
         ImGui::Text("More spacing: Hello"); ImGui::SameLine(0, 20);
-        ImGui::TextColored(ImVec4(1,1,0,1), "Sailor");
+        ImGui::TextColored(ImVec4(1, 1, 0, 1), "Sailor");
 
         // Button
         ImGui::AlignTextToFramePadding();
@@ -3397,6 +3399,36 @@ static void ShowDemoWindowLayout()
 
         ImGui::TreePop();
     }
+
+    IMGUI_DEMO_MARKER("Layout/Overlap Mode");
+    if (ImGui::TreeNode("Overlap Mode"))
+    {
+        static bool enable_allow_overlap = true;
+
+        HelpMarker(
+            "Hit-testing is by default performed in item submission order, which generally is perceived as 'back-to-front'.\n\n"
+            "By using SetNextItemAllowOverlap() you can notify that an item may be overlapped by another. Doing so alters the hovering logic: items using AllowOverlap mode requires an extra frame to accept hovered state.");
+        ImGui::Checkbox("Enable AllowOverlap", &enable_allow_overlap);
+
+        ImVec2 button1_pos = ImGui::GetCursorScreenPos();
+        ImVec2 button2_pos = ImVec2(button1_pos.x + 50.0f, button1_pos.y + 50.0f);
+        if (enable_allow_overlap)
+            ImGui::SetNextItemAllowOverlap();
+        ImGui::Button("Button 1", ImVec2(80, 80));
+        ImGui::SetCursorScreenPos(button2_pos);
+        ImGui::Button("Button 2", ImVec2(80, 80));
+
+        // This is typically used with width-spanning items.
+        // (note that Selectable() has a dedicated flag ImGuiSelectableFlags_AllowOverlap, which is a shortcut
+        // for using SetNextItemAllowOverlap(). For demo purpose we use SetNextItemAllowOverlap() here.)
+        if (enable_allow_overlap)
+            ImGui::SetNextItemAllowOverlap();
+        ImGui::Selectable("Some Selectable", false);
+        ImGui::SameLine();
+        ImGui::SmallButton("++");
+
+        ImGui::TreePop();
+    }
 }
 
 static void ShowDemoWindowPopups()