The document scale factors are now guaranteed to be non-zero.

A new Cairo helper function get_safe_device_factors() and a type
zathura_device_factors_t are introduced to simplify the code and avoid
some #ifdef blocks.

The scale-factor property is more specific than the GDK configure event
and is the recommended way to watch for scale factor changes.

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

This allows fast visual navigation through the 'd'ouble page
shortcut in combination with a high pages-per-row setting.

Resolves #635

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

replaced with gdk_cursor_new_for_display()

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Ideally we would handle this differently. See the TODO entry in the render
function. But the patch is a start.

Thanks to carlos for the patch.

Closes: #398

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Also emit the D-Bus signal

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Thanks to MaximeC for the initial patch.

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>

They are not used anywere, and do not seem to become useful anymore in
the light of the new separation of document and view.

Otherwise the document object gets updated with wrong position values,
because the adjustment belong to the index, not the document view.

The adjustment callbacks act as an interface between position data in
the document object, and the adjustments.

We remove the horizontal centering code, as now it is done by
position_set. Those callbacks should not change the position read from
the document object in any way.

Also, we split the adjustment_value_changed callback into a vertical and
an horizontal version. Previously a single callback was reused for both,
horizontal and vertical. That lead to a subtle problem when coming out
of index mode. What happened was the following:

  1. horizontal adjustment bounds change coming out of index mode. This
     triggers an hadjustment changed signal.

  2. the hadjustment_changed callback handles it, and resets the
     hadjustment value, as the bound may have changed. This triggers a
     value_changed event.

  3. the value_changed callback handles the event, and captures the
     position for *BOTH*, horizontal and vertical adjustments, saving
     them to the document object.

  1..3 is repeated for the vertical adjustment.

  Now, if in 3. the horizontal adjustment bounds were not yet updated
  after the index mode, we got ourselves at the wrong vertical position.

This race condition is avoided now because both value_changed callbacks
*ONLY* handle their own direction, either vertical or horizontal, not
 both.

This new function adjust_view is in charge of recomputing the scale
according to adjustment settings and trigger a render_all.

adjust_view contains the old sc_adjust_window code, slightly simplified
thanks to the availability of the document_get_viewport_size.

Then it is used by sc_adjust_window, document_open and the
cb_view_resized callback. Makes slightly more sense this way than
calling the shortcut sc_adjust_window directly.

Now we can trigger a gtk page refresh calling refresh_view. This
function triggers a custom signal refresh-view, whose handler copies the
position from the document object to the adjustments.

All of those callbacks are conceptually related (change the page
layout), and depend from one another.

Now the single callback page_layout_value_changed defers to
page_widget_set_mode to change whatever is needed in the GTK widgets.

  - fix the computation of the number of rows in the table. Doing a ceil
    of an integer division has no effect...

  - set the page_padding in page_widget_set_mode function, instead of
    doing it independently.

  - call zathura_document_set_layout after calling page_widget_set_mode
    to save the page layout settings into the document object.

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>