fix(widgets): honor rounded panel padding

include/imguix/widgets/containers/rounded_panel.ipp

@@ -344,21 +344,24 @@ namespace ImGuiX::Widgets {
 
         rounded_panel_stack().push_back(state);
 
-        // Keep the override alive across the whole BeginChild/EndChild pair.
-        // Nested RoundedPanel calls naturally follow the ImGui style stack.
+        // WindowPadding configures the child being created. Restore the
+        // caller's style before rendering content so nested windows and
+        // popups keep their own theme metrics.
         ImGui::PushStyleVar(
             ImGuiStyleVar_WindowPadding,
             padding);
 
         const bool child_open = ImGui::BeginChild(
             id,
             panel_size,
-            ImGuiChildFlags_None,
+            ImGuiChildFlags_AlwaysUseWindowPadding,
             ImGuiWindowFlags_NoBackground |
                 ImGuiWindowFlags_NoTitleBar |
                 ImGuiWindowFlags_NoResize |
                 ImGuiWindowFlags_NoCollapse);
 
+        ImGui::PopStyleVar();
+
         if (config.clip_mode ==
                 RoundedPanelClipMode::CoverCorners &&
             border_thickness > 0.0f) {
@@ -413,7 +416,6 @@ namespace ImGuiX::Widgets {
         }
 
         ImGui::EndChild();
-        ImGui::PopStyleVar();
 
         ImDrawList* draw_list =
             ImGui::GetForegroundDrawList();

tests/test_rounded_panel_padding_header_only.cpp

@@ -0,0 +1,76 @@
+#define IMGUIX_HEADER_ONLY
+
+#include <imguix/widgets/containers/rounded_panel.hpp>
+
+#include <imgui.h>
+
+#include <cmath>
+#include <iostream>
+
+namespace {
+
+    bool nearly_equal(const float lhs, const float rhs) {
+        return std::fabs(lhs - rhs) < 0.01f;
+    }
+
+}  // namespace
+
+int main() {
+    ImGui::CreateContext();
+
+    ImGuiIO& io = ImGui::GetIO();
+    io.DisplaySize = ImVec2(640.0f, 480.0f);
+    io.DeltaTime = 1.0f / 60.0f;
+
+    unsigned char* pixels = nullptr;
+    int atlas_width = 0;
+    int atlas_height = 0;
+    io.Fonts->GetTexDataAsRGBA32(&pixels, &atlas_width, &atlas_height);
+
+    ImGuiStyle& style = ImGui::GetStyle();
+    const ImVec2 original_padding = style.WindowPadding;
+    const ImVec2 panel_padding(18.0f, 16.0f);
+
+    ImGui::NewFrame();
+    ImGui::SetNextWindowPos(ImVec2(20.0f, 20.0f));
+    ImGui::SetNextWindowSize(ImVec2(400.0f, 300.0f));
+    ImGui::Begin("##rounded_panel_padding_test", nullptr,
+                 ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_NoResize);
+
+    ImGuiX::Widgets::RoundedPanelConfig config;
+    config.padding = panel_padding;
+    config.border_thickness = 0.0f;
+    config.clip_mode = ImGuiX::Widgets::RoundedPanelClipMode::PaddedContent;
+
+    const bool panel_open =
+        ImGuiX::Widgets::BeginRoundedPanel("##panel", ImVec2(240.0f, 160.0f), config);
+    const ImVec2 child_position = ImGui::GetWindowPos();
+    const ImVec2 content_position = ImGui::GetCursorScreenPos();
+    const ImVec2 active_style_padding = style.WindowPadding;
+
+    ImGuiX::Widgets::EndRoundedPanel();
+    ImGui::End();
+    ImGui::Render();
+
+    const bool content_uses_requested_padding =
+        nearly_equal(content_position.x - child_position.x, panel_padding.x) &&
+        nearly_equal(content_position.y - child_position.y, panel_padding.y);
+    const bool caller_style_restored = nearly_equal(active_style_padding.x, original_padding.x) &&
+                                       nearly_equal(active_style_padding.y, original_padding.y);
+
+    ImGui::DestroyContext();
+
+    if (!panel_open) {
+        std::cerr << "rounded panel child was unexpectedly clipped\n";
+        return 1;
+    }
+    if (!content_uses_requested_padding) {
+        std::cerr << "rounded panel did not apply its requested child padding\n";
+        return 1;
+    }
+    if (!caller_style_restored) {
+        std::cerr << "rounded panel leaked its child padding into caller content\n";
+        return 1;
+    }
+    return 0;
+}