diff --git a/doc/cookbook/clutter-cookbook.xml.in b/doc/cookbook/clutter-cookbook.xml.in index 868b813e0..0c63be1fb 100644 --- a/doc/cookbook/clutter-cookbook.xml.in +++ b/doc/cookbook/clutter-cookbook.xml.in @@ -386,8 +386,7 @@ on_paint (ClutterActor *actor) - Textures @@ -401,6 +400,150 @@ on_paint (ClutterActor *actor) introduction +
+ Drawing 2D graphics onto a texture + +
+ Problem + + You want to draw 2D graphics inside a Clutter application. +
+ +
+ Solution + + Create a ClutterCairoTexture, then draw onto the Cairo context + it wraps using the Cairo API: + + + +ClutterActor *texture; +cairo_t *cr; + +guint width, height; +width = 800; +height = 600; + +texture = clutter_cairo_texture_new (width, height); + +cr = clutter_cairo_texture_create (CLUTTER_CAIRO_TEXTURE (texture)); + +/* + * write onto the Cairo context cr using the Cairo API; + * see the Cairo API reference for details + */ +cairo_move_to (cr, 0, 0); +cairo_line_to (cr, 800, 600); +cairo_stroke (cr); + +/* does the actual drawing onto the texture */ +cairo_destroy (cr); + + + + Here's a useful + Cairo tutorial if you want to learn more about the Cairo API + itself. +
+ +
+ Discussion + + A ClutterCairoTexture is a standard ClutterActor, so it can be + added to ClutterContainers (e.g. a ClutterStage or ClutterGroup), + animated, resized etc. in the usual ways. + + Other useful operations: + + + + + To draw on part of the texture: + use clutter_cairo_texture_create_region to + retrieve a Cairo context for the region you want to draw on. + + + + To clear existing content from a texture: + use clutter_cairo_texture_clear. + + You may need to do this as the texture reuses the same + Cairo context each time you call + clutter_cairo_texture_create or + clutter_cairo_texture_create_region. + + + + To resize the Cairo context wrapped + by a texture, use + clutter_cairo_texture_set_surface_size. + + + + +
+ Drawing pages from a PDF onto a ClutterCairoContext + + Other libraries may provide an API for writing onto a + Cairo context; you can make use of these APIs on the exposed + Cairo context of a ClutterCairoTexture. For example, you + can use the poppler-glib API to display pages + from a PopplerDocument inside a Clutter application: + + + + + +/* snipped setup code (as above) */ + +/* + * cast to CLUTTER_CAIRO_TEXTURE, as the functions + * used below require that type + */ +ClutterCairoTexture *cc_texture = CLUTTER_CAIRO_TEXTURE (texture); + +clutter_cairo_texture_clear (cc_texture); + +gchar *file_uri = "file:///path/to/file.pdf"; +guint page_num = 0; +double page_width, page_height; + +PopplerDocument *doc; +PopplerPage *page; +GError *error = NULL; + +doc = poppler_document_new_from_file (file_uri, NULL, &error); + +page = poppler_document_get_page (doc, page_num); + +poppler_page_get_size (page, &page_width, &page_height); + +cr = clutter_cairo_texture_create (cc_texture); + +/* render the page to the context */ +poppler_page_render (page, cr); + +cairo_destroy (cr); +]]> + + + + Note that if the page is larger than the Cairo context, + some of it might not be visible. Similarly, if the ClutterCairoTexture + is larger than the stage, some of that might not be visible. So you + may need to do some work to make the ClutterCairoTexture fit + inside the stage properly (e.g. resize the stage), and/or some work + to make the PDF page sit inside the Cairo context (e.g. scale the PDF + page or put it inside a scrollable actor). + +
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