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To: jamos@oboj.net, ori@eigenstate.org
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Subject: Re: [9front] Netsurf 3.9 for Plan 9 (work in progress)
Date: Thu, 2 Jan 2020 08:45:47 -0800
From: ori@eigenstate.org
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> On 2020-01-02 00:57, ori@eigenstate.org wrote:
> 
>> I get a garbled image (see attached).
> 
> This is the most common display, alas.
> It is possible to tweak a web page in
> order for it to display slightly more
> beutifully, that is the file 9html/full.html.
> 
> https://webbkurs.ei.hv.se/~imjam/plan9/full_html.png
> 
> This is how full.html looks for me.
> As soon as the bars does not span the whole
> screen, the picture comes out of sync. As
> an interesting note, the test programs for
> the framebuffer driver works as expected
> (e.g. bitmap/plottest/etc.)

I see the problem:

	loaded = loadimage(drawstate->srvimage, r, drawstate->localimage,
			drawstate->imagebytes);

The rectangle here is just the portion of the screen that's changed,
so, eg, a 30x30 icon or something. But drawstate->localimage is the
full view. So, you're uploading the first bunch of pixels of the image
instead of the region you want to draw.

Changing the code to create a rectangle representing the whole local
image and uploading it ungarbles it:

	all.min.x = 0;
	all.min.y = 0;
	all.max.x = 800;
	all.max.y = 600;
	loaded = loadimage(drawstate->srvimage, all, drawstate->localimage,
			drawstate->imagebytes);

For efficiency, we would really want a strided load image, but if there's
a native plan 9 gui, that becoems a moot point.

Other comments:

	box->x0, box->y0, box->x1 - box->x0, box->y1 - box->y0

box is just a 'Rectangle', so you can convert once and just pass the
resulting 'r' around:

	r.min.x = box->x0;
	r.min.y = box->y0;
	r.max.x = box->x1;
	r.max.y = box->y1;
	update_and_redraw_srvimage(drawstate, r);

>> The garbled image doesn't change with
>> respect to window size.
> 
> Yes, the framebuffer size is set at
> initialisation, it is set to 800x600.
> 
> Jonas