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Patric Stout

Fix #6319: [Win32] don't use clipping; draw whole screen every frame (#8726)

When we clip the region that is only been redrawn, something
weird happens on Windows. When pushing 60 frames per second on a
60Hz monitor, it appears that the clipped region is often shown
of another frame, instead of the current.

Examples of this are:
- pause the game, move your mouse to the left, and at the right
speed it totally disappears.
- fast aircrafts seem to be in several places at once, weirdly
lagging behind.
- in title screen, moving your mouse gives you the idea it is
jumping places, instead of smooth movements.

In the end, if you do nothing, everything is correct, so it is
eventually consistent. Just when we are firing many BitBlt in
a clipped region, the in-between is not.

What goes wrong exactly, I honestly do not know. On every frame
that we push to the DC is a mouse painted, but visually it
sometimes appears like it is not. Recording with external software
shows it really is there.
It is also not our eyes playing tricks on us, as the first example
makes it really clear the mouse pointer really is not painted.

And to be clear, with the mouse this is easiest reproduceable,
as high-speed objects are influences by this most. But this happens
for all movement that redraws small regions.

Either way, not using clipped regions resolves the issue completely,
and there appears to be little to no penalty (I failed to measure
any impact of drawing the full screen). So better have a good game
than fast code, I guess?

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file fontdetection.h Functions related to detecting/finding the right font. */

#ifndef FONTDETECTION_H
#define FONTDETECTION_H

#include "fontcache.h"

#ifdef WITH_FREETYPE

#include <ft2build.h>
#include FT_FREETYPE_H

/**
 * Load a freetype font face with the given font name.
 * @param font_name The name of the font to load.
 * @param face The face that has been found.
 * @return The error we encountered.
 */
FT_Error GetFontByFaceName(const char *font_name, FT_Face *face);

#endif /* WITH_FREETYPE */

/**
 * We would like to have a fallback font as the current one
 * doesn't contain all characters we need.
 * This function must set all fonts of settings.
 * @param settings the settings to overwrite the fontname of.
 * @param language_isocode the language, e.g. en_GB.
 * @param winlangid the language ID windows style.
 * @param callback The function to call to check for missing glyphs.
 * @return true if a font has been set, false otherwise.
 */
bool SetFallbackFont(struct FreeTypeSettings *settings, const char *language_isocode, int winlangid, class MissingGlyphSearcher *callback);

#endif