Change: Allow text shadow on WWT_EMPTY/WWT_TEXT to extend horizontally.

[PeterN]

Motivation / Problem

Text shadow of truetype fonts is sometimes cropped when displayed. This is because the shadow isn't included in the width of the text string for truetype fonts, so the widget clipping prevents it from appearing. This does not affect the sprite font which has the shadow baked in and included in the glyph width.

This also only affects text which fits the widget width exactly, or right-aligned text.

Description

This PR allows the text to extend the widget bounds by 1 scaled pixel horizontally. This alleviates text shadows of truetype fonts being cropped in some window layouts. While not technically correct, in most cases this should be sufficient. Note however that this extra scaled pixel is already allowed vertically, which improved shadows on letters with descenders.

To properly include the shadow width in string width calculations so that it matches how the sprite font behaves is likely quite complex to get right as there are multiple layouters with different places to get right/wrong. Simply increasing the character width would make kerning wrong.

Limitations

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker