Fix slider size in compact mode

(cherry picked from commit f21a969bb96f217e144f4a0844bbc71188e4ad04)

editor/themes/editor_theme_manager.cpp

@@ -1419,21 +1419,24 @@ void EditorThemeManager::_populate_standard_styles(const Ref<EditorTheme> &p_the
 		p_theme->set_icon("decrement_highlight", "VScrollBar", empty_icon);
 		p_theme->set_icon("decrement_pressed", "VScrollBar", empty_icon);
 
+		// Slider
+		const int background_margin = MAX(2, p_config.base_margin / 2);
+
 		// HSlider.
 		p_theme->set_icon("grabber_highlight", "HSlider", p_theme->get_icon(SNAME("GuiSliderGrabberHl"), EditorStringName(EditorIcons)));
 		p_theme->set_icon("grabber", "HSlider", p_theme->get_icon(SNAME("GuiSliderGrabber"), EditorStringName(EditorIcons)));
-		p_theme->set_stylebox("slider", "HSlider", make_flat_stylebox(p_config.dark_color_3, 0, p_config.base_margin / 2, 0, p_config.base_margin / 2, p_config.corner_radius));
-		p_theme->set_stylebox("grabber_area", "HSlider", make_flat_stylebox(p_config.contrast_color_1, 0, p_config.base_margin / 2, 0, p_config.base_margin / 2, p_config.corner_radius));
-		p_theme->set_stylebox("grabber_area_highlight", "HSlider", make_flat_stylebox(p_config.contrast_color_1, 0, p_config.base_margin / 2, 0, p_config.base_margin / 2));
+		p_theme->set_stylebox("slider", "HSlider", make_flat_stylebox(p_config.dark_color_3, 0, background_margin, 0, background_margin, p_config.corner_radius));
+		p_theme->set_stylebox("grabber_area", "HSlider", make_flat_stylebox(p_config.contrast_color_1, 0, background_margin, 0, background_margin, p_config.corner_radius));
+		p_theme->set_stylebox("grabber_area_highlight", "HSlider", make_flat_stylebox(p_config.contrast_color_1, 0, background_margin, 0, background_margin));
 		p_theme->set_constant("center_grabber", "HSlider", 0);
 		p_theme->set_constant("grabber_offset", "HSlider", 0);
 
 		// VSlider.
 		p_theme->set_icon("grabber", "VSlider", p_theme->get_icon(SNAME("GuiSliderGrabber"), EditorStringName(EditorIcons)));
 		p_theme->set_icon("grabber_highlight", "VSlider", p_theme->get_icon(SNAME("GuiSliderGrabberHl"), EditorStringName(EditorIcons)));
-		p_theme->set_stylebox("slider", "VSlider", make_flat_stylebox(p_config.dark_color_3, p_config.base_margin / 2, 0, p_config.base_margin / 2, 0, p_config.corner_radius));
-		p_theme->set_stylebox("grabber_area", "VSlider", make_flat_stylebox(p_config.contrast_color_1, p_config.base_margin / 2, 0, p_config.base_margin / 2, 0, p_config.corner_radius));
-		p_theme->set_stylebox("grabber_area_highlight", "VSlider", make_flat_stylebox(p_config.contrast_color_1, p_config.base_margin / 2, 0, p_config.base_margin / 2, 0));
+		p_theme->set_stylebox("slider", "VSlider", make_flat_stylebox(p_config.dark_color_3, background_margin, 0, background_margin, 0, p_config.corner_radius));
+		p_theme->set_stylebox("grabber_area", "VSlider", make_flat_stylebox(p_config.contrast_color_1, background_margin, 0, background_margin, 0, p_config.corner_radius));
+		p_theme->set_stylebox("grabber_area_highlight", "VSlider", make_flat_stylebox(p_config.contrast_color_1, background_margin, 0, background_margin, 0));
 		p_theme->set_constant("center_grabber", "VSlider", 0);
 		p_theme->set_constant("grabber_offset", "VSlider", 0);
 	}