Image(): comment and minor refactor to resurface the fact that a border size may be added. (#2118)

Make more similar to ImageButton()

imgui.h

@@ -532,8 +532,8 @@ namespace ImGui
 
     // Widgets: Images
     // - Read about ImTextureID here: https://github.com/ocornut/imgui/wiki/Image-Loading-and-Displaying-Examples
-    // - Note that ImageButton() adds style.FramePadding*2.0f to provided size. This is in order to facilitate fitting an image in a button.
-    IMGUI_API void          Image(ImTextureID user_texture_id, const ImVec2& size, const ImVec2& uv0 = ImVec2(0, 0), const ImVec2& uv1 = ImVec2(1, 1), const ImVec4& tint_col = ImVec4(1, 1, 1, 1), const ImVec4& border_col = ImVec4(0, 0, 0, 0));
+    // - Note that Image() may add +2.0f to provided size if a border is visible, ImageButton() adds style.FramePadding*2.0f to provided size.
+    IMGUI_API void          Image(ImTextureID user_texture_id, const ImVec2& image_size, const ImVec2& uv0 = ImVec2(0, 0), const ImVec2& uv1 = ImVec2(1, 1), const ImVec4& tint_col = ImVec4(1, 1, 1, 1), const ImVec4& border_col = ImVec4(0, 0, 0, 0));
     IMGUI_API bool          ImageButton(const char* str_id, ImTextureID user_texture_id, const ImVec2& image_size, const ImVec2& uv0 = ImVec2(0, 0), const ImVec2& uv1 = ImVec2(1, 1), const ImVec4& bg_col = ImVec4(0, 0, 0, 0), const ImVec4& tint_col = ImVec4(1, 1, 1, 1));
 
     // Widgets: Combo Box (Dropdown)

imgui_widgets.cpp

@@ -1007,28 +1007,23 @@ bool ImGui::ScrollbarEx(const ImRect& bb_frame, ImGuiID id, ImGuiAxis axis, ImS6
     return held;
 }
 
-void ImGui::Image(ImTextureID user_texture_id, const ImVec2& size, const ImVec2& uv0, const ImVec2& uv1, const ImVec4& tint_col, const ImVec4& border_col)
+void ImGui::Image(ImTextureID user_texture_id, const ImVec2& image_size, const ImVec2& uv0, const ImVec2& uv1, const ImVec4& tint_col, const ImVec4& border_col)
 {
     ImGuiWindow* window = GetCurrentWindow();
     if (window->SkipItems)
         return;
 
-    ImRect bb(window->DC.CursorPos, window->DC.CursorPos + size);
-    if (border_col.w > 0.0f)
-        bb.Max += ImVec2(2, 2);
+    const float border_size = (border_col.w > 0.0f) ? 1.0f : 0.0f;
+    const ImVec2 padding(border_size, border_size);
+    const ImRect bb(window->DC.CursorPos, window->DC.CursorPos + image_size + padding * 2.0f);
     ItemSize(bb);
     if (!ItemAdd(bb, 0))
         return;
 
-    if (border_col.w > 0.0f)
-    {
-        window->DrawList->AddRect(bb.Min, bb.Max, GetColorU32(border_col), 0.0f);
-        window->DrawList->AddImage(user_texture_id, bb.Min + ImVec2(1, 1), bb.Max - ImVec2(1, 1), uv0, uv1, GetColorU32(tint_col));
-    }
-    else
-    {
-        window->DrawList->AddImage(user_texture_id, bb.Min, bb.Max, uv0, uv1, GetColorU32(tint_col));
-    }
+    // Render
+    if (border_size > 0.0f)
+        window->DrawList->AddRect(bb.Min, bb.Max, GetColorU32(border_col), 0.0f, ImDrawFlags_None, border_size);
+    window->DrawList->AddImage(user_texture_id, bb.Min + padding, bb.Max - padding, uv0, uv1, GetColorU32(tint_col));
 }
 
 // ImageButton() is flawed as 'id' is always derived from 'texture_id' (see #2464 #1390)