Re: [evince] dvi text select and mouse-dvi alignment

[Mike Marchywka <marchywka hotmail com>]

On Fri, Oct 25, 2019 at 03:45:29AM -0600, Jason Crain wrote:
> On 10/25/19 3:03 AM, Mike Marchywka via evince-list wrote:
> > 1) The code I found looked like an error, the y-coord was apparently
> > shifted with border.right which sounds incorrect vs say border.top .
> > 2) On the first page without scrolling the above y seems to work ok.
> > 3) With scrolling, the text and mouse seemed to drift at about a 3-4 percent
> > rate hence the nice kluge. I wanted typeset the document as a single ( long )
> > page and aside from the obvious hazards of such a drift this becomes
> > a huge problem here. If this is some kind of fp round off or other known
> > problem it would be nice to fix- alternatively I can track it down as I wanted
> > to look at the coords anyway although hopefully mich later.
> > 4) The use of the view->scale in the empircally working code does not seem
> > consistent, it has a value around
> > 1.2 whcn I looked, and misuse should be an obvious problem
> > even on a normal page.
> >
> > Was text select disabled on dvi for a reason or am I working with
> > very old code, apparently by source download is labelled
> > as evince-3.18.2.
>
> Version 3.18.2 is from 2015. The newest version is 3.34.1. See
> https://wiki.gnome.org/Apps/Evince/Downloads for links to the official
> downloads.
>
> As far as I know, the dvi backend has never supported the text interfaces.
> Only the PDF and DjVu backends currently support it.
>
> There very well may be a bug in evince, though since text selection is
> working fairly well with PDF documents, if there is a bug, it might be
> limited to only the DVI backend.

I guess I forgot I added margins to DviContext and got them from here, 
see last two lines, this is from dvi-document.c. I have no idea
if these are baked into the other quantities somewhere,

static cairo_surface_t *
dvi_document_render (EvDocument      *document,
                     EvRenderContext *rc)
{
        cairo_surface_t *surface;
        cairo_surface_t *rotated_surface;
        DviDocument *dvi_document = DVI_DOCUMENT(document);
        gdouble xscale, yscale;
        gint required_width, required_height;
        gint proposed_width, proposed_height;
        gint xmargin = 0, ymargin = 0;

        /* We should protect our context since it's not 
         * thread safe. The work to the future - 
         * let context render page independently
         */
        g_mutex_lock (&dvi_context_mutex);

        mdvi_setpage (dvi_document->context, rc->page->index);

        ev_render_context_compute_scales (rc, dvi_document->base_width, dvi_document->base_height,
                                          &xscale, &yscale);
        mdvi_set_shrink (dvi_document->context,
                         (int)((dvi_document->params->hshrink - 1) / xscale) + 1,
                         (int)((dvi_document->params->vshrink - 1) / yscale) + 1);

        ev_render_context_compute_scaled_size (rc, dvi_document->base_width, dvi_document->base_height,
                                               &required_width, &required_height);
        proposed_width = dvi_document->context->dvi_page_w * dvi_document->context->params.conv;
        proposed_height = dvi_document->context->dvi_page_h * dvi_document->context->params.vconv;

        if (required_width >= proposed_width)
            xmargin = (required_width - proposed_width) / 2;
        if (required_height >= proposed_height)
            ymargin = (required_height - proposed_height) / 2;

        mdvi_cairo_device_set_margins (&dvi_document->context->device, xmargin, ymargin);
        mdvi_cairo_device_set_scale (&dvi_document->context->device, xscale, yscale);
        mdvi_cairo_device_render (dvi_document->context);
        surface = mdvi_cairo_device_get_surface (&dvi_document->context->device);
        dvi_document->context->xmargin=xmargin; // mjm 
        dvi_document->context->ymargin=ymargin; // mjm 




> _______________________________________________
> evince-list mailing list
> evince-list gnome org
> https://mail.gnome.org/mailman/listinfo/evince-list

-- 

mike marchywka
306 charles cox
canton GA 30115
USA, Earth 
marchywka hotmail com
404-788-1216
ORCID: 0000-0001-9237-455X