61 lines
1.9 KiB
Go
61 lines
1.9 KiB
Go
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// +build ignore
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// (ignored pending Go issues 7409 and 7548)
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// x+build !windows,!darwin,!plan9
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// 14 march 2014
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package ui
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import (
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"image"
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)
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// #cgo pkg-config: gtk+-3.0
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// #include <gtk/gtk.h>
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// extern gboolean our_draw_callback(GtkWidget *, cairo_t *, gpointer);
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import "C"
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func gtkAreaNew() *gtkWidget {
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drawingarea := C.gtk_drawing_area_new()
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scrollarea := C.gtk_scrolled_window_new((*C.GtkAdjustment)(nil), (*C.GtkAdjustment)(nil))
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// need a viewport because GtkDrawingArea isn't natively scrollable
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C.gtk_scrolled_window_add_with_viewport(scrollarea, drawingarea)
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return fromgtkwidget(scrollarea)
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}
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//export our_draw_callback
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func our_draw_callback(widget *C.GtkWidget, cr *C.cairo_t, data C.gpointer) C.gboolean {
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var x, y, w, h C.double
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s := (*sysData)(unsafe.Pointer(data))
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// thanks to desrt in irc.gimp.net/#gtk+
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C.cairo_clip_extents(cr, &x, &y, &w, &h)
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cliprect := image.Rect(int(x), int(y), int(w), int(h))
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imgret := make(chan *image.NRGBA)
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defer close(imgret)
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s.paint <- PaintRequest{
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Rect: cliprect,
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Out: imgret,
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}
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i := <-imgret
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// pixel order is [R G B A] (see Example 1 on https://developer.gnome.org/gdk-pixbuf/2.26/gdk-pixbuf-The-GdkPixbuf-Structure.html) so we don't have to convert anything
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// gdk-pixbuf is not alpha-premultiplied (thanks to desrt in irc.gimp.net/#gtk+)
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pixbuf := C.gdk_pixbuf_new_from_data(
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(*C.guchar)(unsafe.Pointer(&i.Pix[0])),
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C.GDK_COLORSPACE_RGB,
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C.TRUE, // has alpha channel
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8, // bits per sample
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C.int(i.Rect.Dx()),
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C.int(i.Rect.Dy()),
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C.int(i.Stride),
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nil, nil) // do not free data
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C.gdk_cairo_set_source_pixbuf(cr,
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pixbuf,
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C.gdouble(cliprect.Min.X),
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C.gdouble(cliprect.Min.Y))
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C.g_object_unref((C.gpointer)(unsafe.Pointer(pixbuf))) // free pixbuf
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return C.FALSE // TODO what does this return value mean? docs don't say
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}
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var draw_callback = C.GCallback(C.our_draw_callback)
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