diff options
| -rw-r--r-- | areaplan.md | 34 |
1 files changed, 25 insertions, 9 deletions
diff --git a/areaplan.md b/areaplan.md index 1247613..0296844 100644 --- a/areaplan.md +++ b/areaplan.md @@ -181,12 +181,16 @@ We can use `GtkDrawingArea`. We hook into the `draw` signal; it does something e ```go func draw_callback(widget *C.GtkWidget, cr *C.cairo_t, data C.gpointer) C.gboolean { + var x, y, w, h C.double + s := (*sysData)(unsafe.Pointer(data)) - // TODO get clip rectangle that needs drawing + // thanks to desrt in irc.gimp.net/#gtk+ + C.cairo_clip_extents(cr, &x, &y, &w, &h) + cliprect := image.Rect(int(x), int(y), int(w), int(h)) imgret := make(chan *image.NRGBA) defer close(imgret) s.paint <- PaintRequest{ - Rect: /* clip rect */, + Rect: cliprect, Out: imgret, } i := <-imgret @@ -201,21 +205,33 @@ func draw_callback(widget *C.GtkWidget, cr *C.cairo_t, data C.gpointer) C.gboole nil, nil) // do not free data C.gdk_cairo_set_source_pixbuf(cr, pixbuf, - /* x of clip rect */, - /* y of clip rect */) + C.gdouble(cliprect.Min.X), + C.gdouble(cliprect.Min.Y)) + C.g_object_unref((C.gpointer)(unsafe.Pointer(pixbuf))) // free pixbuf return C.FALSE // TODO what does this return value mean? docs don't say } ``` -TODO delete pixbuf - -TODO is the gdk-pixbuf alpha-premultiplied? +[Example 1 on this page](https://developer.gnome.org/gdk-pixbuf/2.26/gdk-pixbuf-The-GdkPixbuf-Structure.html) indicates the pixels are in RGBA order, which is good. -TODO verify pixel order +On alpha premultiplication: +``` +12:27 andlabs Hi. Is the pixel data fed to gdk-pixbuf alpha premultiplied, not alpha premultiplied, or is that settable? I need to feed it data from a source that doesn't know about the underlying rendering system. Thanks. +12:29 *** KaL_out is now known as KaL +12:29 desrt andlabs: pixbuf is non-premultiplied +12:30 mclasen sad that this information is not obvious in the docs +12:30 andlabs there is no information about premultiplied in any of the GTK+ documentation, period +12:30 desrt andlabs: we have a utility function to copy it to a cairo surface that does the multiply for you... +12:30 andlabs (in versions compatible with ubuntu 12.04, at least) +12:31 andlabs good to know, thanks +12:31 desrt andlabs: i think it's because gdkpixbuf existed before premultiplication was a wide practice +12:31 desrt so at the time nobody would have asked the question +12:31 andlabs huh +``` TODO figure out how scrolling plays into this -TODO double-check docs to see that the clip rect is cleared before the draw event is issued +TODO "Note that GDK automatically clears the exposed area to the background color before sending the expose event" decide what to do for the other platforms ## Cocoa For this one we **must** create a subclass of `NSView` that overrides the drawing and keyboard/mouse event messages. |