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Features/GTK3/Porting (view source)
Revision as of 14:47, 11 November 2011
, 14:47, 11 November 2011→Tips to Activity Developers
<pre>
<pre>
# From activity.Activity, you inherit a canvas. Get its window.
win = self.canvas.get_window()
# Create a Cairo context from the window.
cairo_context = win.cairo_create()
# Create a Cairo surface from the context
surface = cairo_context.get_target()
# Create an XLib surface to be used for drawing
xlib_surface = surface.create_similar(cairo.CONTENT_COLOR,
gtk.gdk.screen_width(),
gtk.gdk.screen_height())
# You'll need a Cairo context from which you'll build a GTK Cairo context
cairo_context = cairo.Context(xlib_surface)
cairo_context = gtk.gdk.CairoContext(cairo_context)
# Use this context as you would a Drawable, substituting Cairo commands
# for gtk commands, e.g.,
cairo_context.move_to(0, 0)
cairo_context.line_to(100, 100)
# Cairo uses floats from 0 to 1 for RGB values
cairo_context.set_source_rgb(r, g, b)
cairo_context.rectangle(x, y, w, h)
cairo_context.fill()
# To invalidate a region to force a refresh, use:
self.canvas.queue_draw_area(x, y, w, h)
</pre>
</pre>
Pango is a bit different when used with Cairo:
Pango is a bit different when used with Cairo:
<pre>
<pre>
# Again, from the xlib_surface...
cairo_context = cairo.Context(xlib_surface)
# Create a PangoCairo context
cairo_context = pangocairo.CairoContext(cairo_context)
# The pango layout is created from the Cairo context
pango_layout = cairo_context.create_layout()
# You still use pango to set up font descriptions.
fd = pango.FontDescription('Sans')
fd.set_size(12 * pango.SCALE)
# Tell your pango layout about your font description
pango_layout.set_font_description(fd)
# Write text to your pango layout
pango_layout.set_text('Hello world')
# Position it within the Cairo context
cairo_context.save()
cairo_context.translate(x, y)
cairo_context.rotate(pi / 3) # You can rotate text and images in Cairo
cairo_context.set_source_rgb(1, 0, 0)
# Finally, draw the text
cairo_context.update_layout(pango_layout)
cairo_context.show_layout(pango_layout)
cairo_context.restore()
</pre>
</pre>
<pre>
<pre>
# Again, from the xlib_surface...
cairo_context = cairo.Context(xlib_surface)
# Create a gtk context
cairo_context = gtk.gdk.CairoContext(cairo_context)
cairo_context.set_source_pixbuf(pixbuf, x, y)
cairo_context.rectangle(x, y, w, h)
cairo_context.fill()
</pre>
</pre>
<pre>
<pre>
# Map the xlib surface onto a pixmap
pixmap = gtk.gdk.Pixmap(None, w, h, 24)
cairo_context = pixmap.cairo_create()
cairo_context.set_source_surface(xlib_surface, 0, 0)
cairo_context.paint()
# Read the pixel
pixel = pixmap.get_image(x, y, 1, 1).get_pixel(0, 0)
return(int((pixel & 0xFF0000) >> 16), # red
int((pixel & 0x00FF00) >> 8), # green
int((pixel & 0x0000FF) >> 0), 0) # blue
</pre>
</pre>
The Cairo/Pango interaction is a little different:
The Cairo/Pango interaction is a little different:
<pre>
<pre>
cairo_context = ...
pango_layout = PangoCairo.create_layout(cairo_context)
pango_layout.set_font_description(fd)
pango_layout.set_text('Hello World', -1)
cairo_context.set_source_rgb(1, 0, 0)
PangoCairo.update_layout(cairo_context, pango_layout)
PangoCairo.show_layout(cairo_context, pango_layout)
</pre>
</pre>