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More Area planning.

This commit is contained in:
Pietro Gagliardi 2014-03-14 12:40:47 -04:00
parent 21d3bf944b
commit 502522b0a6
1 changed files with 25 additions and 9 deletions
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34
areaplan.md
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@ -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
[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 is the gdk-pixbuf alpha-premultiplied?
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.