HiDPI scaling (gtk3) - Githubissues

cass00 commented 8 years ago

Xournalpp (gtk3) doesn't cope with hidpi scaling properly. If I go from normal scaling to hidpi scaling, with say a scaling factor of 2, all objects become twice as big (same zoom level) and lines appear blurry.

I guess Xournalpp is currently not taking this setting into account resulting in this undesired behavior. Any suggestions where the code has to be changed to include this feature? It works fine in Inkscape and Gimp. Maybe these programs can provide a clue on how to handle this scaling factor.

andreasb242 commented 8 years ago

All graphics are kept in a buffer image, so the view is only repainted if you really change, and not on scrolling.

I would guess this buffer is the problem. I have no high DPI device to check...

Look at https://github.com/xournalpp/xournalpp/blob/master/src/control/jobs/PreviewJob.cpp

void PreviewJob::run() { XOJ_CHECK_TYPE(PreviewJob);

=>> Not sure what GTK3 returns here... GtkAllocation alloc; gtk_widget_get_allocation(this->sidebarPreview->widget, &alloc);

=>> Multiple the size with the HDPI Scale? cairo_surface_t* crBuffer = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, alloc.width, alloc.height);

double zoom = this->sidebarPreview->sidebar->getZoom();

cairo_t* cr2 = cairo_create(crBuffer);
cairo_matrix_t defaultMatrix = { 0 };
cairo_get_matrix(cr2, &defaultMatrix);

cairo_translate(cr2, Shadow::getShadowTopLeftSize() + 2,
                Shadow::getShadowTopLeftSize() + 2);

=>> Divide the size with the HDPI Scale? cairo_scale(cr2, zoom, zoom);

cass00 commented 8 years ago

Cheers, I'll look into it when I got time. Btw. I think you can activate the high DPI setting even if you're not having a high DPI device. Everything is just a bit bigger then :)

cass00 commented 8 years ago

As a note: There is cairo_surface_set_device_scale () which was added for this purpose from what I've read (see Cairo ref).

andreasb242 commented 8 years ago

OK, but I have no time next week...

cass00 commented 8 years ago

An easy way to test xournalpp under HiDPI conditions is to use the GDK_SCALE parameter e.g. GDK_SCALE=2 xournalpp -w No need to change any global settings.

cass00 commented 8 years ago

Had a little deeper look into this. It seems there is a bit more work needed. Again, evince might provide the answer to what has to be changed. The relevant commits should be GNOME/evince@a612f809e4e, GNOME/evince@37c13b386a8915 and GNOME/evince@2d3feb111939.

andreasb242 commented 8 years ago

The preview size should also be adapted, but it shouldn’t be that much...

cass00 commented 8 years ago

I made a bit of progress by introducing a scale factor in commit cass00/xournalpp@74c86fbbc2c0d6816. However, not working yet: -scaling of PDF background -strokes not sharp while writing (they become sharp after they are rendered again) -pages are not of equal size for same zoom levels between high dpi and normal (works in evince) -other parts that are affected by rescaling

Furthermore, there is a zoom calibration tab in the preference (the one with the ruler). The scaling factor from there however doesn't seem to have any effect/ is not used. Maybe it would be a good time to integrate this one as well now.

cass00 commented 8 years ago

Managed to get strokes and pdf text (not pictures in pdf) sharp as well. However, I realized that there are tons of other cairo surfaces, for example for imported images or the selection tool. Potentially all of them have to made aware of the display scale. One tricky example is in pixbuf-utils.cpp: surface = cairo_image_surface_create_for_data(pixels, format, width, height, width * size); Simple rescaling doesn't seem to work here. If anyone has some input, please let me know.