Demo: Added more complete Combo demo. (#1658)

TODO.txt

@@ -237,6 +237,7 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - font: fix AddRemapChar() to work before font has been built.
  - font: (api breaking) removed "TTF" from symbol names. also because it now supports OTF.
 
+ - nav: SetItemDefaultFocus() level of priority, so widget like Selectable when inside a popup could claim a low-priority default focus on the first selected iem
  - nav: allow input system to be be more tolerant of io.DeltaTime=0.0f
  - nav: ESC on a flattened child
  - nav: Left within a tree node block as a fallback (ImGuiTreeNodeFlags_NavLeftJumpsBackHere by default?)

imgui_demo.cpp

@@ -321,37 +321,16 @@ void ImGui::ShowDemoWindow(bool* p_open)
                 ImGui::EndTooltip();
             }
 
-            // Testing ImGuiOnceUponAFrame helper.
-            //static ImGuiOnceUponAFrame once;
-            //for (int i = 0; i < 5; i++)
-            //    if (once)
-            //        ImGui::Text("This will be displayed only once.");
-
             ImGui::Separator();
 
             ImGui::LabelText("label", "Value");
 
             {
-                // Simplified one-liner Combo() API, using values packed in a single constant string
+                // Using the _simplified_ one-liner Combo() api here
-                static int current_item_1 = 1;
+                const char* items[] = { "AAAA", "BBBB", "CCCC", "DDDD", "EEEE", "FFFF", "GGGG", "HHHH", "IIII", "JJJJ", "KKKK", "LLLLLLL", "MMMM", "OOOOOOO" };
-                ImGui::Combo("combo", &current_item_1, "aaaa\0bbbb\0cccc\0dddd\0eeee\0\0");
+                static int item_current = 0;
-                //ImGui::Combo("combo w/ array of char*", &current_item_2_idx, items, IM_ARRAYSIZE(items));   // Combo using proper array. You can also pass a callback to retrieve array value, no need to create/copy an array just for that.
+                ImGui::Combo("combo", &item_current, items, IM_ARRAYSIZE(items));
-
+                ImGui::SameLine(); ShowHelpMarker("Refer to the \"Combo\" section below for an explanation of the full BeginCombo/EndCombo API, and demonstration of various flags.\n");
-                // General BeginCombo() API, you have full control over your selection data and display type
-                const char* items[] = { "AAAA", "BBBB", "CCCC", "DDDD", "EEEE", "FFFF", "GGGG", "HHHH", "IIII", "JJJJ", "KKKK", "LLLLLLL", "MMMM", "OOOOOOO", "PPPP", "QQQQQQQQQQ", "RRR", "SSSS" };
-                static const char* current_item_2 = NULL;
-                if (ImGui::BeginCombo("combo 2", current_item_2)) // The second parameter is the label previewed before opening the combo.
-                {
-                    for (int n = 0; n < IM_ARRAYSIZE(items); n++)
-                    {
-                        bool is_selected = (current_item_2 == items[n]); // You can store your selection however you want, outside or inside your objects
-                        if (ImGui::Selectable(items[n], is_selected))
-                            current_item_2 = items[n];
-                        if (is_selected)
-                            ImGui::SetItemDefaultFocus();   // Set the initial focus when opening the combo (scrolling + for keyboard navigation support in the upcoming navigation branch)
-                    }
-                    ImGui::EndCombo();
-                }
             }
 
             {
@@ -394,13 +373,17 @@ void ImGui::ShowDemoWindow(bool* p_open)
                 ImGui::SliderAngle("slider angle", &angle);
             }
 
+            {
                 static float col1[3] = { 1.0f,0.0f,0.2f };
                 static float col2[4] = { 0.4f,0.7f,0.0f,0.5f };
                 ImGui::ColorEdit3("color 1", col1);
                 ImGui::SameLine(); ShowHelpMarker("Click on the colored square to open a color picker.\nRight-click on the colored square to show options.\nCTRL+click on individual component to input value.\n");
 
                 ImGui::ColorEdit4("color 2", col2);
+            }
 
+            {
+                // List box
                 const char* listbox_items[] = { "Apple", "Banana", "Cherry", "Kiwi", "Mango", "Orange", "Pineapple", "Strawberry", "Watermelon" };
                 static int listbox_item_current = 1;
                 ImGui::ListBox("listbox\n(single select)", &listbox_item_current, listbox_items, IM_ARRAYSIZE(listbox_items), 4);
@@ -409,10 +392,17 @@ void ImGui::ShowDemoWindow(bool* p_open)
                 //ImGui::PushItemWidth(-1);
                 //ImGui::ListBox("##listbox2", &listbox_item_current2, listbox_items, IM_ARRAYSIZE(listbox_items), 4);
                 //ImGui::PopItemWidth();
+            }
 
             ImGui::TreePop();
         }
 
+        // Testing ImGuiOnceUponAFrame helper.
+        //static ImGuiOnceUponAFrame once;
+        //for (int i = 0; i < 5; i++)
+        //    if (once)
+        //        ImGui::Text("This will be displayed only once.");
+
         if (ImGui::TreeNode("Trees"))
         {
             if (ImGui::TreeNode("Basic trees"))
@@ -617,6 +607,49 @@ void ImGui::ShowDemoWindow(bool* p_open)
             ImGui::TreePop();
         }
 
+        if (ImGui::TreeNode("Combo"))
+        {
+            // Expose flags as checkbox for the demo
+            static ImGuiComboFlags flags = 0;
+            ImGui::CheckboxFlags("ImGuiComboFlags_PopupAlignLeft", (unsigned int*)&flags, ImGuiComboFlags_PopupAlignLeft);
+            if (ImGui::CheckboxFlags("ImGuiComboFlags_NoArrowButton", (unsigned int*)&flags, ImGuiComboFlags_NoArrowButton))
+                flags &= ~ImGuiComboFlags_NoPreview;     // Clear the other flag, as we cannot combine both
+            if (ImGui::CheckboxFlags("ImGuiComboFlags_NoPreview", (unsigned int*)&flags, ImGuiComboFlags_NoPreview))
+                flags &= ~ImGuiComboFlags_NoArrowButton; // Clear the other flag, as we cannot combine both
+
+            // General BeginCombo() API, you have full control over your selection data and display type.
+            // (your selection data could be an index, a pointer to the object, an id for the object, a flag stored in the object itself, etc.)
+            const char* items[] = { "AAAA", "BBBB", "CCCC", "DDDD", "EEEE", "FFFF", "GGGG", "HHHH", "IIII", "JJJJ", "KKKK", "LLLLLLL", "MMMM", "OOOOOOO" };
+            static const char* item_current = items[0];            // Here our selection is a single pointer stored outside the object.
+            if (ImGui::BeginCombo("combo 1", item_current, flags)) // The second parameter is the label previewed before opening the combo.
+            {
+                for (int n = 0; n < IM_ARRAYSIZE(items); n++)
+                {
+                    bool is_selected = (item_current == items[n]);
+                    if (ImGui::Selectable(items[n], is_selected))
+                        item_current = items[n];
+                    if (is_selected)
+                        ImGui::SetItemDefaultFocus();   // Set the initial focus when opening the combo (scrolling + for keyboard navigation support in the upcoming navigation branch)
+                }
+                ImGui::EndCombo();
+            }
+
+            // Simplified one-liner Combo() API, using values packed in a single constant string
+            static int item_current_2 = 0; 
+            ImGui::Combo("combo 2 (one-liner)", &item_current_2, "aaaa\0bbbb\0cccc\0dddd\0eeee\0\0");
+
+            // Simplified one-liner Combo() using an array of const char*
+            static int item_current_3 = -1; // If the selection isn't within 0..count, Combo won't display a preview
+            ImGui::Combo("combo 3 (array)", &item_current_3, items, IM_ARRAYSIZE(items));
+
+            // Simplified one-liner Combo() using an accessor function
+            struct FuncHolder { static bool ItemGetter(void* data, int idx, const char** out_str) { *out_str = ((const char**)data)[idx]; return true; } };
+            static int item_current_4 = 0;
+            ImGui::Combo("combo 4 (function)", &item_current_4, &FuncHolder::ItemGetter, items, IM_ARRAYSIZE(items));
+
+            ImGui::TreePop();
+        }
+
         if (ImGui::TreeNode("Selectables"))
         {
             // Selectable() has 2 overloads: