docking feature + example (#6)

* feat: docking feature + example

imgui = { version, features = ["docking"] }:
- sources switch to upstream's docking tag (compat.imgui 1.92.8-docking, a
  superset — identical behavior with the feature off; default build/tests
  unchanged).
- core exports the Dock* surface gated by MCPP_FEATURE_DOCKING
  (DockSpace/DockSpaceOverViewport/SetNextWindowDockID/GetWindowDockID/
  IsWindowDocked + ConfigFlags_DockingEnable/Cond_FirstUseEver constants;
  plain-int typedefs intentionally not re-aliased — GMF typedef name clash).
- imgui.app facade auto-enables ImGuiConfigFlags_DockingEnable.
- examples/docking: pre-docked Toolbox/Inspector via DockSpaceOverViewport
  (verified rendering: docked tab bar). CI builds it (needs mcpp >= 0.0.47
  for features; CI installs latest).

* ci: bootstrap mcpp 0.0.48 (features mechanism required by docking example)

---------

Co-authored-by: sunrisepeak <x.d2learn.org@gmail.com>

Author: Sunrisepeak

.github/workflows/ci.yml

@@ -102,3 +102,9 @@ jobs:
         run: |
           cd examples/glfw_opengl3
           mcpp build
+
+      - name: Build docking example (features=["docking"])
+        shell: bash
+        run: |
+          cd examples/docking
+          mcpp build

.xlings.json

@@ -1,5 +1,5 @@
 {
   "workspace": {
-    "xim:mcpp": "0.0.44"
+    "xim:mcpp": "0.0.48"
   }
 }

README.md

@@ -41,6 +41,21 @@ alias — the rest of the consumer code is identical. Cross-platform GL/GLSL
 configuration (incl. macOS forward-compat) is handled by `RecommendedGlConfig()`,
 which `CreateWindow`/`Init` use by default.
 
+## Features
+
+- `docking` — exports the Dock* API surface (`DockSpace`, `DockSpaceOverViewport`,
+  `SetNextWindowDockID`, `IsWindowDocked`, ...) and makes the `imgui.app` facade
+  enable `ImGuiConfigFlags_DockingEnable` automatically:
+
+  ```toml
+  [dependencies]
+  imgui = { version = "0.0.4", features = ["docking"] }
+  ```
+
+  See `examples/docking/`. Sources come from upstream's docking tag
+  (`compat.imgui 1.92.8-docking`, a superset of mainline — identical behavior
+  while the feature is off).
+
 ## Dependencies
 
 The root package depends on:

examples/docking/mcpp.toml

@@ -0,0 +1,8 @@
+[package]
+name        = "imgui-docking"
+version     = "0.1.0"
+description = "Dockable-windows demo using the imgui `docking` feature"
+license     = "MIT"
+
+[dependencies]
+imgui = { path = "../..", features = ["docking"] }

examples/docking/src/main.cpp

@@ -0,0 +1,26 @@
+// Docking demo — `imgui = { ..., features = ["docking"] }`.
+// The imgui.app facade auto-enables ImGuiConfigFlags_DockingEnable when the
+// feature is active; DockSpaceOverViewport turns the whole window into a
+// dock host, so the two panels below can be dragged into / split around it.
+import imgui.core;
+import imgui.app;
+
+int main() {
+    return ImGui::App::run({.title = "mcpp imgui docking demo"}, [] {
+        const auto dockspace = ImGui::DockSpaceOverViewport();
+
+        // Pre-dock both panels into the dockspace on first run; they remain
+        // freely draggable/splittable afterwards.
+        ImGui::SetNextWindowDockID(dockspace, ImGui::Cond_FirstUseEver);
+        ImGui::Begin("Toolbox");
+        ImGui::TextUnformatted("Drag this panel onto the dockspace.");
+        ImGui::TextUnformatted("Docked: ");
+        ImGui::TextUnformatted(ImGui::IsWindowDocked() ? "yes" : "no");
+        ImGui::End();
+
+        ImGui::SetNextWindowDockID(dockspace, ImGui::Cond_FirstUseEver);
+        ImGui::Begin("Inspector");
+        ImGui::TextUnformatted("Split me against the Toolbox.");
+        ImGui::End();
+    });
+}

mcpp.toml

@@ -22,8 +22,14 @@ sources = [
   "src/backends/opengl3_impl.cpp",
 ]
 
+[features]
+default = []
+# docking: export the Dock* API surface and auto-enable
+# ImGuiConfigFlags_DockingEnable in the imgui.app facade.
+docking = []
+
 [dependencies]
-compat.imgui = "1.92.8"
+compat.imgui = "1.92.8-docking"
 compat.glfw = "3.4"
 compat.opengl = "2026.05.31"
 

src/app.cppm

@@ -53,6 +53,10 @@ export namespace ImGui::App {
 
         ImGuiContext* context = ImGui::CreateContext();
         ImGui::SetCurrentContext(context);
+#ifdef MCPP_FEATURE_DOCKING
+        // `docking` feature: enable dockable windows out of the box.
+        ImGui::GetIO().ConfigFlags |= ImGui::ConfigFlags_DockingEnable;
+#endif
 
         if (!Backend::Init(window)) {
             const auto error = Backend::LastError();

src/core.cppm

@@ -26,3 +26,25 @@ export namespace ImGui {
     using ::ImGui::SetCurrentContext;
     using ::ImGui::TextUnformatted;
 }
+
+// Docking surface — gated by the `docking` feature
+// (`imgui = { ..., features = ["docking"] }`). Requires the upstream docking
+// sources (compat.imgui 1.92.8-docking); with the feature off, the docking
+// sources behave exactly like mainline.
+#ifdef MCPP_FEATURE_DOCKING
+// (ImGuiID / ImGuiDockNodeFlags are plain-integer typedefs; GMF typedefs
+//  cannot be re-aliased under the same global name in a module. Consumers
+//  take DockSpace* return values with `auto`.)
+export namespace ImGui {
+    using ::ImGui::DockSpace;
+    using ::ImGui::DockSpaceOverViewport;
+    using ::ImGui::SetNextWindowDockID;
+    using ::ImGui::GetWindowDockID;
+    using ::ImGui::IsWindowDocked;
+
+    // Unscoped global enumerators, re-exported as namespaced constants for
+    // module consumers.
+    inline constexpr int ConfigFlags_DockingEnable = ::ImGuiConfigFlags_DockingEnable;
+    inline constexpr int Cond_FirstUseEver         = ::ImGuiCond_FirstUseEver;
+}
+#endif