Add font scaling to studio, bound to CTRL+MINUS/PLUS

PiperOrigin-RevId: 907491215
Change-Id: I144467c3ff0e3d11f4a5bfb6ed2b1e4e88b8693d

src/experimental/platform/ux/gui.cc

@@ -213,15 +213,32 @@ void SetupTheme(GuiTheme theme) {
   s.DockingNodeHasCloseButton = false;
 }
 
+void RescaleDock(float ratio) {
+  if (ratio == 1) return;
+  ImGuiID root = ImGui::GetID("Root");
+  ImGuiDockNode* root_node = ImGui::DockBuilderGetNode(root);
+  if (root_node) {
+    struct ScaleNodes {
+      static void Apply(ImGuiDockNode* node, float r) {
+        node->SizeRef.x *= r;
+        if (node->ChildNodes[0]) Apply(node->ChildNodes[0], r);
+        if (node->ChildNodes[1]) Apply(node->ChildNodes[1], r);
+      }
+    };
+    ScaleNodes::Apply(root_node, ratio);
+  }
+}
+
 ImVec4 ConfigureDockingLayout() {
   ImGuiViewport* viewport = ImGui::GetMainViewport();
   const float scale = ImGui::GetWindowDpiScale();
+  const float font_scale = ImGui::GetIO().FontGlobalScale;
 
   const float kOptionsRelWidth = 0.22f;
   const float kInspectorRelWidth = 0.22f;
   const float kStatsRelHeight = 0.3f;
-  const float kToolsBarHeight = 36.f * scale;
-  const float kStatusBarHeight = 32.f * scale;
+  const float kToolsBarHeight = 36.f * scale * font_scale;
+  const float kStatusBarHeight = 32.f * scale * font_scale;
 
   const ImVec2 dockspace_pos{viewport->WorkPos.x,
                              viewport->WorkPos.y + kToolsBarHeight};
@@ -303,6 +320,7 @@ ImVec4 ConfigureDockingLayout() {
     platform::ScopedStyle style;
     style.Var(ImGuiStyleVar_WindowBorderSize, 1.0f);
     style.Var(ImGuiStyleVar_WindowRounding, 0.0f);
+    style.Var(ImGuiStyleVar_WindowMinSize, ImVec2(1, 1));
     const float toolbar_vpad =
         std::max(0.f, (kToolsBarHeight - ImGui::GetFrameHeight()) * 0.5f);
     style.Var(ImGuiStyleVar_WindowPadding, ImVec2(4, toolbar_vpad));
@@ -318,6 +336,7 @@ ImVec4 ConfigureDockingLayout() {
     platform::ScopedStyle style;
     style.Var(ImGuiStyleVar_WindowBorderSize, 1.0f);
     style.Var(ImGuiStyleVar_WindowRounding, 0.0f);
+    style.Var(ImGuiStyleVar_WindowMinSize, ImVec2(1, 1));
     ImGui::SetNextWindowPos(ImVec2(0, viewport->Size.y - kStatusBarHeight),
                             ImGuiCond_Always);
     ImGui::SetNextWindowSize(ImVec2(viewport->Size.x, kStatusBarHeight),

src/experimental/platform/ux/gui.h

@@ -42,6 +42,9 @@ enum class GuiTheme {
 // Updates the ImGui internal style state to match the requested theme.
 void SetupTheme(GuiTheme theme);
 
+// Rescales all dock node widths by the given ratio.
+void RescaleDock(float ratio);
+
 // Configures the ImGui docking module to the standard layout used by Studio.
 // This includes the following named sections:
 //   "ToolBar": fixed size bar spanning the top of the window; for placing

src/experimental/studio/app.cc

@@ -578,6 +578,14 @@ void App::HandleKeyboardEvents() {
     tmp_.inspector_panel = !tmp_.inspector_panel;
   } else if (ImGui_IsChordJustPressed(ImGuiKey_Tab)) {
     tmp_.options_panel = !tmp_.options_panel;
+  } else if (ImGui_IsChordJustPressed(ImGuiKey_Minus | ImGuiMod_Ctrl)) {
+    float old_scale = ui_.font_scale;
+    ui_.font_scale = std::clamp(ui_.font_scale - 0.1f, 0.5f, 3.0f);
+    platform::RescaleDock(ui_.font_scale / old_scale);
+  } else if (ImGui_IsChordJustPressed(ImGuiKey_Equal | ImGuiMod_Ctrl)) {
+    float old_scale = ui_.font_scale;
+    ui_.font_scale = std::clamp(ui_.font_scale + 0.1f, 0.5f, 3.0f);
+    platform::RescaleDock(ui_.font_scale / old_scale);
   } else if (ImGui_IsChordJustPressed(ImGuiKey_Minus)) {
     SetSpeedIndex(tmp_.speed_index + 1);
   } else if (ImGui_IsChordJustPressed(ImGuiKey_Equal)) {
@@ -823,6 +831,8 @@ void App::BuildGui() {
     platform::SetupTheme(ui_.theme);
   }
 
+  ImGui::GetIO().FontGlobalScale = ui_.font_scale;
+
   const ImVec4 workspace_rect = platform::ConfigureDockingLayout();
 
   // Place charts in bottom right corner of the workspace.
@@ -1841,11 +1851,13 @@ float App::GetExpectedLabelWidth() {
 App::UiState::Dict App::UiState::ToDict() const {
   return {
       {"theme", std::to_string(static_cast<int>(theme))},
+      {"font_scale", std::to_string(font_scale)},
   };
 }
 
 void App::UiState::FromDict(const Dict& dict) {
   *this = UiState();
   theme = ReadIniValue(dict, "theme", theme);
+  font_scale = platform::ReadIniValue(dict, "font_scale", font_scale);
 }
 }  // namespace mujoco::studio

src/experimental/studio/app.h

@@ -105,6 +105,7 @@ class App {
     int camera_idx = platform::kTumbleCameraIdx;
     int key_idx = 0;
     platform::GuiTheme theme = platform::GuiTheme::kLight;
+    float font_scale = 1.0f;
 
     using Dict = std::unordered_map<std::string, std::string>;
     Dict ToDict() const;