1 files changed, 127 insertions, 0 deletions
diff --git a/src/ui/widget/optglarea.cpp b/src/ui/widget/optglarea.cpp
new file mode 100644
index 0000000..72ec362
--- /dev/null
+++ b/src/ui/widget/optglarea.cpp
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <cassert>
+#include "optglarea.h"
+
+namespace Inkscape {
+namespace UI {
+namespace Widget {
+
+OptGLArea::OptGLArea()
+{
+    set_app_paintable(true); // No problem for GTK4 port since this whole widget will be deleted.
+    opengl_enabled = false;
+}
+
+void OptGLArea::on_realize()
+{
+    Gtk::DrawingArea::on_realize();
+    if (opengl_enabled) init_opengl();
+}
+
+void OptGLArea::on_unrealize()
+{
+    if (context) {
+        if (framebuffer) {
+            context->make_current();
+            delete_framebuffer();
+        }
+        if (context == Gdk::GLContext::get_current()) {
+            Gdk::GLContext::clear_current(); // ?
+        }
+        context.reset();
+    }
+    Gtk::DrawingArea::on_unrealize();
+}
+
+void OptGLArea::on_size_allocate(Gtk::Allocation &allocation)
+{
+    Gtk::DrawingArea::on_size_allocate(allocation);
+    if (get_realized()) need_resize = true;
+}
+
+void OptGLArea::set_opengl_enabled(bool enabled)
+{
+    if (opengl_enabled == enabled) return;
+    opengl_enabled = enabled;
+    if (opengl_enabled && get_realized()) init_opengl();
+}
+
+void OptGLArea::init_opengl()
+{
+    context = create_context();
+    if (!context) opengl_enabled = false;
+    framebuffer = 0;
+    need_resize = true;
+}
+
+void OptGLArea::make_current()
+{
+    assert(context);
+    context->make_current();
+}
+
+bool OptGLArea::on_draw(const Cairo::RefPtr<Cairo::Context> &cr)
+{
+    if (opengl_enabled) {
+        context->make_current();
+
+        if (!framebuffer) {
+            create_framebuffer();
+        }
+
+        if (need_resize) {
+            resize_framebuffer();
+            need_resize = false;
+        }
+
+        paint_widget(cr);
+
+        int s = get_scale_factor();
+        int w = get_allocated_width() * s;
+        int h = get_allocated_height() * s;
+        gdk_cairo_draw_from_gl(cr->cobj(), get_window()->gobj(), renderbuffer, GL_RENDERBUFFER, s, 0, 0, w, h);
+
+        context->make_current(); // ?
+    } else {
+        paint_widget(cr);
+    }
+
+    return true;
+}
+
+void OptGLArea::bind_framebuffer() const
+{
+    assert(context);
+    glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
+    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderbuffer);
+    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, stencilbuffer);
+}
+
+void OptGLArea::create_framebuffer()
+{
+    glGenFramebuffers (1, &framebuffer);
+    glGenRenderbuffers(1, &renderbuffer);
+    glGenRenderbuffers(1, &stencilbuffer);
+}
+
+void OptGLArea::delete_framebuffer()
+{
+    glDeleteRenderbuffers(1, &renderbuffer);
+    glDeleteRenderbuffers(1, &stencilbuffer);
+    glDeleteFramebuffers (1, &framebuffer);
+}
+
+void OptGLArea::resize_framebuffer() const
+{
+    int s = get_scale_factor();
+    int w = get_allocated_width() * s;
+    int h = get_allocated_height() * s;
+    glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
+    glRenderbufferStorage(GL_RENDERBUFFER, GL_RGB8, w, h);
+    glBindRenderbuffer(GL_RENDERBUFFER, stencilbuffer);
+    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, w, h);
+}
+
+} // namespace Widget
+} // namespace UI
+} // namespace Inkscape