FittedCanvas: a GtkCanvas wrapper that follows ui-scale and ignores child size requests

gtk2_ardour/fitted_canvas_widget.cc

@@ -0,0 +1,85 @@
+/*
+    Copyright (C) 2019 Paul Davis
+    Author: Ben Loftis <ben@harrisonconsoles.com>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include <algorithm>
+#include <cairomm/context.h>
+
+#include <pangomm/layout.h>
+
+#include "pbd/compose.h"
+
+#include "gtkmm2ext/keyboard.h"
+#include "gtkmm2ext/utils.h"
+
+#include "canvas/canvas.h"
+#include "canvas/debug.h"
+#include "canvas/utils.h"
+
+#include "actions.h"
+#include "gui_thread.h"
+#include "utils.h"
+#include "timers.h"
+
+#include "fitted_canvas_widget.h"
+
+using namespace std;
+using namespace ArdourCanvas;
+using namespace Gtk;
+using namespace Gtkmm2ext;
+using namespace ARDOUR_UI_UTILS;
+
+
+//a gtk widget with fixed-size semantics
+FittedCanvasWidget::FittedCanvasWidget (float w, float h, bool follow_scale)
+{
+	_nominal_width = w;
+	_nominal_height = h;
+	_follow_scale = follow_scale;
+
+	//our rendering speed suffers if we re-render knobs simply because they are in-between 2 meters that got invalidated (for example)
+//	set_single_exposure(false);
+//#ifdef __APPLE__
+//	use_intermediate_surface (false);
+//#endif
+}
+
+void
+FittedCanvasWidget::on_size_request (Gtk::Requisition* req)
+{
+	const double scale = _follow_scale ? UIConfiguration::instance().get_ui_scale() : 1;
+	if (_nominal_width>0) {
+		req->width = _nominal_width*scale;
+	}
+	if (_nominal_height>0) {
+		req->height = _nominal_height*scale;
+	}
+}
+
+
+void
+FittedCanvasWidget::on_size_allocate (Gtk::Allocation& alloc)
+{
+	GtkCanvas::on_size_allocate(alloc);
+
+	if (!_root.items().empty()) {
+		ArdourCanvas::Item *fitted = *_root.items().begin();
+		fitted->size_allocate(ArdourCanvas::Rect(0,0,alloc.get_width(), alloc.get_height()));
+	}
+}
+

gtk2_ardour/fitted_canvas_widget.h

@@ -0,0 +1,67 @@
+/*
+    Copyright (C) 2021 Paul Davis
+    Author: Ben Loftis <ben@harrisonconsoles.com>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#ifndef __fitted_canvas_widget__
+#define __fitted_canvas_widget__
+
+#include <string>
+#include <vector>
+
+#include <pangomm/fontdescription.h>
+
+#include <canvas/canvas.h>
+#include <canvas/container.h>
+#include <canvas/item.h>
+#include <canvas/fill.h>
+#include <canvas/outline.h>
+#include <canvas/rectangle.h>
+
+#include <gtkmm/layout.h>
+
+#include <ardour/route.h>
+#include <ardour/plugin.h>
+#include <ardour/plugin_insert.h>
+#include <ardour/automation_control.h>
+
+#include "route_ui.h"
+
+/* FittedCanvasWidget has these properties:
+ *  it is provided a 'nominal size' on construction, which it will request of gtk
+ *  if asked, will resize itself when the user gui/font scale changes
+ *  it 'fits' the Item that was first attached to Root  (presumably the top-level widget or container)
+ *    the fitted Item will be explicitly resized to fit when the canvas size is allocated
+ *    the fitted Item may be a container; it should allocate child positions during size_allocate()
+ *  */
+
+class FittedCanvasWidget : public ArdourCanvas::GtkCanvas
+{
+public:
+	/* per gtk convention you may use -1 for width OR height if you don't care about that dimension */
+	FittedCanvasWidget(float nominal_width, float nominal_height, bool follow_scale=true);
+
+	void on_size_request (Gtk::Requisition* req);  //always returns the nominal size, regardless of children
+	void on_size_allocate (Gtk::Allocation& alloc);
+
+private:
+	float _nominal_width;
+	float _nominal_height;
+	bool  _follow_scale;
+};
+
+#endif //__fitted_canvas_widget__

gtk2_ardour/wscript

@@ -120,6 +120,7 @@ gtk2_ardour_sources = [
         'export_preset_selector.cc',
         'export_report.cc',
         'export_timespan_selector.cc',
+        'fitted_canvas_widget.cc',
         'fft.cc',
         'fft_graph.cc',
         'fft_result.cc',