In article
<[email protected]>,
Chris Young <[email protected]> wrote:
> content_redraw makes me very confused, and there doesn't seem to be
> any documentation on it. Furthermore, my values always appear to be
> "inverted" compared to eg the RISC OS implementation (the first four
> and the second four coordinates are swapped, otherwise I get no output
> or the wrong output).
I asked jmb, adrianl and joty about it and have come up with:
--------------------------------------------------------------------------
struct os_box {
int x0;
int y0;
int x1;
iny y1;
};
struct wimp_draw {
wimp_w w;
os_box box;
int xscroll;
int yscroll;
os_box clip;
};
os_box box - The 'visible work area', the portion of window contents
that's shown.
os_box clip - The region to be redrawn
xscroll - How far the window is scrolled down
yscroll - How far the window is scrolled left
| NOTE: For an os_box:
| - (x0, y0) is bottom left
| - (x1, y1) is top right
| - coordinate origin at bottom left of screen,
| +ve y upwards, +ve x right
| - units are 2 per px
|
| However in NetSurf:
| - (x0, y0) is top left
| - (x1, y1) is bottom right
| - coordinate origin at top left of page,
| +ve y downwards, +ve x right
| - units are px
So in riscos/window.c, ro_gui_window_redraw:
ro_plot_origin_x = redraw->box.x0 - redraw->xscroll;
ro_plot_origin_y = redraw->box.y1 - redraw->yscroll;
Gets the coordinates of the top left of the area of the page/canvas
which is at the top left of the visible area.
clip_x0 = (redraw->clip.x0 - ro_plot_origin_x) / 2;
clip_y0 = (ro_plot_origin_y - redraw->clip.y1) / 2;
clip_x1 = (redraw->clip.x1 - ro_plot_origin_x) / 2;
clip_y1 = (ro_plot_origin_y - redraw->clip.y0) / 2;
Gets the area of the page/canvas requested for redraw in NetSurf units,
from top left of visible content display area:
left: clip_x0
top: clip_y0
right: clip_x1
bottom: clip_y1
These are used to call
plot.clip(clip_x0, clip_y0, clip_x1, clip_y1);
which sets up the clip rectangle for the plotters, and
content_redraw(c, 0, 0,
c->width * scale, c->height * scale,
clip_x0, clip_y0, clip_x1, clip_y1,
g->bw->scale,
0xFFFFFF);
the arguments to which are:
c content of type CONTENT_HTML
x coordinate for top-left of redraw
y coordinate for top-left of redraw
width width
height height
clip_x0 clip rectangle
clip_y0 clip rectangle
clip_x1 clip rectangle
clip_y1 clip rectangle
scale scale for redraw
background_colour the background colour
The 'while(more)' thing is because the RISC OS Wimp gives one
rectangle at a time to have redrawn and you need to check for more
rectangles until there are none.
--------------------------------------------------------------------------
Does that help at all? Are there other bits which are uninteligable?
Cheers,
Michael
--
Michael Drake (tlsa) http://www.netsurf-browser.org/
