highgui: wayland: expand image width if title bar cannot be shown

modules/highgui/src/window_wayland.cpp

@@ -570,6 +570,9 @@ class cv_wl_viewer : public cv_wl_widget {
     cv::Rect last_img_area_;
     bool image_changed_ = false;
 
+    int real_img_width = 0;
+    cv::Scalar const outarea_color_ = CV_RGB(0, 0, 0);
+
     void *param_ = nullptr;
     CvMouseCallback callback_ = nullptr;
 };
@@ -1535,6 +1538,28 @@ void cv_wl_viewer::set_image(cv::Mat const &image) {
         image_ = image.clone();
     }
     image_changed_ = true;
+
+    // See https://github.com/opencv/opencv/issues/25560
+    // If image_ width is too small enough to show title and buttons, expand it.
+
+    // Keep real image width to limit x position for callback functions
+    real_img_width = image_.size().width;
+
+    // Minimum width of title is not defined, so use button width * 3 instead of it.
+    const int view_min_width = cv_wl_titlebar::btn_width * 3 + cv_wl_titlebar::titlebar_min_width;
+
+    const int margin = view_min_width - real_img_width;
+    if(margin > 0)
+    {
+        copyMakeBorder(image_,               // src
+                       image_,               // dst
+                       0,                    // top
+                       0,                    // bottom
+                       0,                    // left
+                       margin,               // right
+                       cv::BORDER_CONSTANT,  // borderType
+                       outarea_color_ );     // value(color)
+    }
 }
 
 void cv_wl_viewer::set_mouse_callback(CvMouseCallback callback, void *param) {
@@ -1587,6 +1612,8 @@ void cv_wl_viewer::on_mouse(int event, cv::Point const &p, int flag) {
             int x = static_cast<int>((p.x - last_img_area_.x) * ((double) image_.size().width / last_img_area_.width));
             int y = static_cast<int>((p.y - last_img_area_.y) *
                                      ((double) image_.size().height / last_img_area_.height));
+
+            x = cv::min(x, real_img_width);
             callback_(event, x, y, flag, param_);
         }
     }

modules/highgui/test/test_gui.cpp

@@ -205,6 +205,21 @@ TEST(Highgui_GUI, trackbar)
     EXPECT_NO_THROW(destroyAllWindows());
 }
 
+// See https://github.com/opencv/opencv/issues/25560
+#if !defined(ENABLE_PLUGINS)
+TEST(Highgui_GUI, DISABLED_small_width_image)
+#else
+TEST(Highgui_GUI, small_width_image)
+#endif
+{
+    const std::string window_name("trackbar_test_window");
+    cv::Mat src(1,1,CV_8UC3,cv::Scalar(0));
+    EXPECT_NO_THROW(destroyAllWindows());
+    ASSERT_NO_THROW(namedWindow(window_name));
+    ASSERT_NO_THROW(imshow(window_name, src));
+    EXPECT_NO_THROW(waitKey(10));
+    EXPECT_NO_THROW(destroyAllWindows());
+}
 
 TEST(Highgui_GUI, currentUIFramework)
 {