[Commits] [SCM] claws branch, gtk3, updated. 3.16.0-741-g0b14aad

[ticho at claws-mail.org]

The branch, gtk3 has been updated
       via  0b14aad2d4be65b524f13e87380d7c92916d42dd (commit)
      from  3c7b518b7b9e265a96a8bd437a8f3bddb6623dbc (commit)

Summary of changes:
 src/plugins/litehtml_viewer/lh_widget.cpp |   29 +++++++++++++++++++++++------
 src/plugins/litehtml_viewer/lh_widget.h   |    3 +++
 2 files changed, 26 insertions(+), 6 deletions(-)


- Log -----------------------------------------------------------------
commit 0b14aad2d4be65b524f13e87380d7c92916d42dd
Author: Andrej Kacian <ticho at claws-mail.org>
Date:   Sun May 5 13:48:09 2019 +0200

    Make litehtml plugin rendering work better with GTK3 widget redraw
    
    Unlike GTK2's "expose-event", GTK3's "draw" signal provides the
    handler function with an already prepared cairo context to draw
    on. This fixes flickering when scrolling HTML messages.
    
    Unfortunately, litehtml's redraw() doesn't allow us to pass
    custom arguments, so we have to store a pointer to the cairo
    context as a member variable of our document container, so that
    redraw() can access it.

diff --git a/src/plugins/litehtml_viewer/lh_widget.cpp b/src/plugins/litehtml_viewer/lh_widget.cpp
index 355e75f..0dbfcf5 100644
--- a/src/plugins/litehtml_viewer/lh_widget.cpp
+++ b/src/plugins/litehtml_viewer/lh_widget.cpp
@@ -108,6 +108,8 @@ lh_widget::lh_widget()
 
 	m_showing_url = FALSE;
 
+	m_cairo_context = NULL;
+
 	gtk_widget_set_events(m_drawing_area,
 			        GDK_BUTTON_RELEASE_MASK
 			      | GDK_BUTTON_PRESS_MASK
@@ -255,16 +257,23 @@ void lh_widget::redraw(gboolean force_render)
 				m_html->width(), m_html->height());
 	}
 
-	gdkwin = gtk_widget_get_window(m_drawing_area);
-	if (gdkwin == NULL) {
-		g_warning("lh_widget::redraw: No GdkWindow to draw on!");
-		return;
+	/* Use provided cairo context, if any. Otherwise create our own. */
+	if (m_cairo_context != NULL) {
+		cr = m_cairo_context;
+	} else {
+		gdkwin = gtk_widget_get_window(m_drawing_area);
+		if (gdkwin == NULL) {
+			g_warning("lh_widget::redraw: No GdkWindow to draw on!");
+			return;
+		}
+		cr = gdk_cairo_create(gdkwin);
 	}
-	cr = gdk_cairo_create(gdkwin);
 
 	draw(cr);
 
-	cairo_destroy(cr);
+	/* Only destroy the used cairo context if we created it earlier. */
+	if (m_cairo_context == NULL)
+		cairo_destroy(cr);
 }
 
 void lh_widget::paint_white()
@@ -479,12 +488,20 @@ GdkPixbuf *lh_widget::get_local_image(const litehtml::tstring url) const
 	return NULL;
 }
 
+void lh_widget::set_cairo_context(cairo_t *cr)
+{
+	m_cairo_context = cr;
+}
+
+
 ////////////////////////////////////////////////
 static gboolean draw_cb(GtkWidget *widget, cairo_t *cr,
 		gpointer user_data)
 {
 	lh_widget *w = (lh_widget *)user_data;
+	w->set_cairo_context(cr);
 	w->redraw(false);
+	w->set_cairo_context(NULL);
 	return FALSE;
 }
 
diff --git a/src/plugins/litehtml_viewer/lh_widget.h b/src/plugins/litehtml_viewer/lh_widget.h
index 9b95ef8..378d80a 100644
--- a/src/plugins/litehtml_viewer/lh_widget.h
+++ b/src/plugins/litehtml_viewer/lh_widget.h
@@ -69,6 +69,8 @@ class lh_widget : public container_linux
 		void set_partinfo(MimeInfo *partinfo);
 		GdkPixbuf *get_local_image(const litehtml::tstring url) const;
 
+		void set_cairo_context(cairo_t *cr);
+
 		litehtml::document::ptr m_html;
 		litehtml::tstring m_clicked_url;
 		litehtml::tstring m_base_url;
@@ -86,6 +88,7 @@ class lh_widget : public container_linux
 		litehtml::element::ptr m_over_element;
 		gboolean m_showing_url;
 		MimeInfo *m_partinfo;
+		cairo_t *m_cairo_context;
 
 		litehtml::tchar_t *m_font_name;
 		int m_font_size;

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