Do not let Emacs rescale the grid tiles

[demoj1]

The grid tiles are made with create-image and no :scale, but the header image passes :scale 1. So Emacs scales only the tiles, by image-scaling-factor. Its default is auto, which means char-width / 10.

My font is Iosevka at 19.6pt, so one character is 13px wide and the factor is 1.3.

Both the header and the grid come from the same column-width, but then the grid is stretched by 30% and the header is not. Each column moves a bit further away from its day name.

Measured on 2a03d9d (emacs -Q, empty backend, only the font set):

	step
day names in the header	136px
column lines in the grid	176px

176 / 136 = 1.29, which is the scaling factor.

With :scale 1 on the tiles, the columns are 135px and line up with the header:

Note that this is not fixed by org-timegrid-default-zoom. Your zoom makes the drawing inside the SVG bigger, and image-scaling-factor stretches the finished image on top of that. The two just multiply.

Nothing changes for users whose character is under 10px wide, because the factor was already 1 for them.

Tests: 30 pass.

[Gleek]

The code looks good. Thanks.

I'm wondering why is the misalignment still there in your fixed screenshot. Is this your scroll bar on the left that shifts the timegrid to the right?

Also the now line doesn't appear. Not sure why that would be happening.

Anyway, merging this.

[Gleek]

Also the now line doesn't appear. Not sure why that would be happening.

This is fixed. Emacs uses X11 colours that SVG can't always recognize. Have passed it through a convertor which now renders the colours correctly.

[demoj1]

Thanks for merging!

Is this your scroll bar on the left that shifts the timegrid to the right?

Yes, exactly that. window-edges reports a 24px gap on my window: an 8px fringe and a 16px scroll bar. I build Emacs with the Lucid toolkit, where the vertical scroll bar is on the left. The header line starts at the window edge, but the tiles are text and start after the scroll bar, so the header was 16px to the left of the grid.

The column step was already correct, so the header was shifted as a whole. That is why it looked like a small constant error and not a growing one.

Opened #5 for it: it measures the gap with window-edges instead of counting the fringe, which also covers the margin and a scroll bar on either side. After the fix the day names sit exactly on the column centres.

Also the now line doesn't appear.

Good catch on the X11 colours, and thanks for fixing it — the red line renders here now.