Demo: Improved trees in columns demo. (#2136)

docs/CHANGELOG.txt

@@ -89,6 +89,7 @@ Other Changes:
 - Misc: Added IM_MALLOC/IM_FREE macros mimicking IM_NEW/IM_DELETE so user doesn't need to revert
   to using the ImGui::MemAlloc()/MemFree() calls directly.
 - Metrics: Added "Show windows rectangles" tool to visualize the different rectangles.
+- Demo: Improved trees in columns demo.
 - Examples: OpenGL: Added a dummy GL call + comments in ImGui_ImplOpenGL3_Init() to detect uninitialized
   GL function loaders early, and help users understand what they are missing. (#2421)
 - Examples: Emscripten: Added Emscripten+SDL+GLES2 example. (#2494, #2492, #2351, #336) [@nicolasnoble, @redblobgames]

imgui_demo.cpp

@@ -2545,16 +2545,39 @@ static void ShowDemoWindowColumns()
         ImGui::TreePop();
     }
 
-    bool node_open = ImGui::TreeNode("Tree within single cell");
-    ImGui::SameLine(); HelpMarker("NB: Tree node must be poped before ending the cell. There's no storage of state per-cell.");
-    if (node_open)
+    if (ImGui::TreeNode("Tree"))
     {
-        ImGui::Columns(2, "tree items");
-        ImGui::Separator();
-        if (ImGui::TreeNode("Hello")) { ImGui::BulletText("Sailor"); ImGui::TreePop(); } ImGui::NextColumn();
-        if (ImGui::TreeNode("Bonjour")) { ImGui::BulletText("Marin"); ImGui::TreePop(); } ImGui::NextColumn();
+        ImGui::Columns(2, "tree", true);
+        for (int x = 0; x < 3; x++)
+        {
+            bool open1 = ImGui::TreeNode((void*)(intptr_t)x, "Node%d", x);
+            ImGui::NextColumn();
+            ImGui::Text("Node contents");
+            ImGui::NextColumn();
+            if (open1)
+            {
+                for (int y = 0; y < 5; y++)
+                {
+                    bool open2 = ImGui::TreeNode((void*)(intptr_t)y, "Node%d.%d", x, y);
+                    ImGui::NextColumn();
+                    ImGui::Text("Node contents");
+                    if (open2)
+                    {
+                        ImGui::Text("Even more contents");
+                        if (ImGui::TreeNode("Tree in column"))
+                        {
+                            ImGui::Text("The quick brown fox jumps over the lazy dog");
+                            ImGui::TreePop();
+                        }
+                    }
+                    ImGui::NextColumn();
+                    if (open2)
+                        ImGui::TreePop();
+                }
+                ImGui::TreePop();
+            }
+        }
         ImGui::Columns(1);
-        ImGui::Separator();
         ImGui::TreePop();
     }
 

imgui_internal.h

@@ -346,7 +346,7 @@ enum ImGuiSelectableFlagsPrivate_
     ImGuiSelectableFlags_NoHoldingActiveID  = 1 << 10,
     ImGuiSelectableFlags_PressedOnClick     = 1 << 11,
     ImGuiSelectableFlags_PressedOnRelease   = 1 << 12,
-    ImGuiSelectableFlags_DrawFillAvailWidth = 1 << 13,
+    ImGuiSelectableFlags_DrawFillAvailWidth = 1 << 13,  // FIXME: We may be able to remove this (added in 6251d379 for menus)
     ImGuiSelectableFlags_AllowItemOverlap   = 1 << 14
 };