>
> From: Oliver.Rauch@Wolfsburg.DE
>
> > b) ___Gamma Curve data is corrupted.___
> > When turning on table-based gamma correction (and thus instantiating the
> > gamma curve widget), the following happen:
> > o correct values are read from the (microtek) backend, so far so good.
> > o immediately after the call to gtk_curve_set_gamma in curve_new(),
> > a call to gtk_curve_get_gamma reveals the correct values were
> > written to the widget.
> > o sometime later (when the event loop updates/displays the widget, I
> > imagine), xscanimage declares
> I already have seen this, too. I hope I will find the time to take a closer
> look at it soon!
>
>
> Hi Oliver, et al.,
>
> For no good reason, I went poking at this with gdb (well, at least I'm
> learning how to use gdb), and made some discoveries. The problem is in
> the widgets, not xscanimage. Someone who knows more about GTK widget
> programming will need to take over from here....
>
> When xscanimage runs, the corruption to the gamma curve widget happens
> during the call to gtk_widget_show(notebook) at the end of vector_new()
> ["gtkglue.c"]. Here are before and after snapshots of the Curve:
>
> BEFORE:
>
> $36 = {graph = {widget = {object = {klass = 0x809b578, flags = 67328,
> ref_count = 1, object_data = 0x8087690}, private_flags = 0,
> state = 0 '\000', saved_state = 0 '\000', name = 0x0, style = 0x8084368,
> requisition = {width = 262, height = 262}, allocation = {x = -1, y = -1,
> width = 1, height = 1}, window = 0x0, parent = 0x809b308},
> draw_data = 0x0}, cursor_type = 132, min_x = 0, max_x = 255, min_y = 0,
> max_y = 255, pixmap = 0x0, curve_type = GTK_CURVE_TYPE_FREE, height = 255,
> grab_point = -1, last = 0, num_points = 256, point = 0x809ba48,
> num_ctlpoints = 2, ctlpoint = 0x809ba30}
>
> AFTER:
>
> $37 = {graph = {widget = {object = {klass = 0x809b578, flags = 329664,
> ref_count = 1, object_data = 0x8095660}, private_flags = 0,
> state = 0 '\000', saved_state = 0 '\000', name = 0x0, style = 0x809d5f8,
> requisition = {width = 262, height = 262}, allocation = {x = -1, y = -1,
> width = 1, height = 1}, window = 0x809d3d8, parent = 0x809b308},
> draw_data = 0x0}, cursor_type = 132, min_x = 0, max_x = 255, min_y = 0,
> max_y = 255, pixmap = 0x809d960, curve_type = GTK_CURVE_TYPE_FREE,
> height = -5, grab_point = -1, last = 0, num_points = -5, point = 0x809d540,
> num_ctlpoints = 2, ctlpoint = 0x809ba30}
>
>
> Note how "height" and "num_points" are now the unlikely values of -5, and
> the "point" vector has moved.
>
> The basic problem is that "allocation.width" and "allocation.height" are 1,1
> and not 262,262. The chain of events (I believe) is: [in "gtk/gtkcurve.c"]
>
> gtk_curve_graph_events() is called for either a CONFIGURE or EXPOSE event,
> and subsequently calls gtk_curve_draw() with the width and height taken
> from the "allocation", as:
> width = w->allocation.width - RADIUS * 2;
> height = w->allocation.height - RADIUS * 2;
> i.e. -5 and -5
>
> gtk_curve_draw() sees the requested width,height (-5,-5) doesn't match what
> was loaded into it (256,256), and calls gtk_curve_interpolate(), which then
> generates screwy numbers.
>
>
> SO: Perhaps gtk_curve_graph_events() should use the curve's "requisition"
> instead of its "allocation" to calculate those width and height.
> Perhaps in an earlier incarnation of GTK, the curve widget got 'allocated'
> earlier or something.
> I don't really know what design issues are involved here.
>
>
> Whatever the solution is, I'd love to hear it, just to get some more insights
> into the workings of GTK.
>
> Hope this is a good head-start,
> -matt m.
Please report it to the authors of gtk and gimp!
They are the ones that should be working on this problem.
Hugo.
+------------------------+------------------------------+
| Hugo van der Kooij | Hugo.van.der.Kooij@caiw.nl |
| Oranje Nassaustraat 16 | http://www.caiw.nl/~hvdkooij |
| 3155 VJ Maasland | (De man met de rode hoed) |
+------------------------+------------------------------+
"Computers let you make more mistakes faster than any other invention in
human history, with the possible exception of handguns and tequila."
(Mitch Radcliffe)
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