Codechange: Remove direct access to _colour_gradient.

Access is now through GetColourGradient, which ensures parameters are in range.

Change: make for smooth-scrolling based on actual time

This means if rendering takes a bit longer, scrolling goes a bit
quicker, making travel time always about the same time for the
same distance.

Codechange: Replace mishmash of types for widget index with WidgetID.

Indices were stored as int, but often passed around as uint/uint8_t and casts.

Now they should all use WidgetID.

Fix #11577: Extra viewport opened in wrong location. (#11578)

ExtraViewportWindow calls IninitializeViewport() with focus as 0, which is ambiguous as focus should be either a TileIndex or a VehicleID.

Instead, pass the tile and let InitializeViewport() handle setting all the coordinates.

Remove: ZOOM_LVL_COUNT

This is the only enumeration with a COUNT and END. The logic of the COUNT
implied that BEGIN could be non-zero, but all but two uses of zoom level
assume that BEGIN is zero, making the separate count only confusing.

Codechange: Remove FONT_HEIGHT_... macros. (#11481)

These make it look like we're dealing with a constant, but actually each is a call to `GetCharacterHeight(...)`.

Codechange: automatic adding of _t to (u)int types, and WChar to char32_t

for i in `find src -type f|grep -v 3rdparty/fmt|grep -v 3rdparty/catch2|grep -v 3rdparty/opengl|grep -v stdafx.h`; do sed 's/uint16& /uint16 \&/g;s/int8\([ >*),;[]\)/int8_t\1/g;s/int16\([ >*),;[]\)/int16_t\1/g;s/int32\([ >*),;[]\)/int32_t\1/g;s/int64\([ >*),;[]\)/int64_t\1/g;s/ uint32(/ uint32_t(/g;s/_uint8_t/_uint8/;s/Uint8_t/Uint8/;s/ft_int64_t/ft_int64/g;s/uint64$/uint64_t/;s/WChar/char32_t/g;s/char32_t char32_t/char32_t WChar/' -i $i; done

Codechange: Make SpriteType, CargoSortType, SourceType and ScriptType enum classes. (#10663)

This avoids a (soft) namespace conflict between the four ST_* enums.

Codechange: instead of global pointer to stack variable, just put variable in that global

Removes one indirection and a dangling pointer to a stack location

Fix #10150: Force FS_SMALL for small viewport signs. (#10283)

* Fix #10150: Force FS_SMALL for small viewport signs.

This is a workaround for string widths being different with mixed
font-sizes.

* Fix: Flag small sign shadow as small text.

(This method of drawing shadows is hilarious and needs replacing, but
this is a quick fix.)

Fix #10151: Use smaller padding for viewport signs. (#10272)

Before variable-scaling, the padding was always 1x1 pixel. This was
changed to be scaled, except using the wrong dimension of 2x1 pixels
instead of 1x1 pixel.

Codechange: Let the compile generate the master command table out of templated command traits.

This is using a non-intrusive type-traits like templated system, which
allows compile-time validation that the command table and the command
enum match up.

Codechange: reference a string by its name, not with "another + 1" (#9517)

It is wrong anyway, as "TINY" normally is at -1. Just weird code.

Codechange: use IterateFromBack/Front only if the order is important.

Use Iterate if the order does not matter.

Codechange: use iterators instead of 'subranges' when iterating from a specific window.

Using iterators makes it easier to include or exclude the start window in the iteration.

Codechange: Apply coding style (#8640)

* Fix: Missing or needed spaces

* Codechange: Remove space

* Codechange: Remove space

* Codechange: More missing spaces

* Codechange: Missing spaces

* Codechange: Remove space

* Codechange: Remove space

Codechange: Spell 'Viewport' consistently

Some places in the codebase misspell 'Viewport' as 'ViewPort' or 'view_port'.
This patch makes everything consistent.

Fix #6566: Fix signed integer overflow in viewport draw area chunking

This caused drawing areas larger than 2097151 pixels at 8x zoom to
not be subdivided into smaller chunks as required.
This resulted in pathological performance issues in the sprite sorter.

Fix #7847: Use ViewportSign coordinates for sign Kdtree coordinates (#7849)

Ensure the same coordinates are used for station/town/player signs regardless of how the landscape changes below it after the coordinates were first determined.

By keeping track of whether each ViewportSign is valid for Kdtree use (and only ever registering the viewport sign when the object is valid) a lot of code can be simplified and become more robust at the same time.

Add #6887: Option to show zone inside local authority boundary of towns

Can be found at town information > local authority window
Layout for button is same as Graph Keys
Turn on/off for every town individually

Fix #7386: Measurement tooltip for tunnels, aqueducts & docks did not display or flickered.

Measurement tooltip was auto-closed as the hover/right-click test for tooltips was not
satisfied in this case. This is fixed by keeping the tooltip visible and instead explicitly
closing the tooltip when the PlaceObject is cancelled/completed.

Remove: ENABLE_NETWORK switch

This switch has been a pain for years. Often disabling broke
compilation, as no developer compiles OpenTTD without, neither do
any of our official binaries.

Additionaly, it has grown so hugely in our codebase, that it
clearly shows that the current solution was a poor one. 350+
instances of "#ifdef ENABLE_NETWORK" were in the code, of which
only ~30 in the networking code itself. The rest were all around
the code to do the right thing, from GUI to NewGRF.

A more proper solution would be to stub all the functions, and
make sure the rest of the code can simply assume network is
available. This was also partially done, and most variables were
correct if networking was disabled. Despite that, often the #ifdefs
were still used.

With the recent removal of DOS, there is also no platform anymore
which we support where networking isn't working out-of-the-box.

All in all, it is time to remove the ENABLE_NETWORK switch. No
replacement is planned, but if you feel we really need this option,
we welcome any Pull Request which implements this in a way that
doesn't crawl through the code like this diff shows we used to.

Fix #7004: Mark linkgraph dirty to be rebuilt on next draw call. (#7265)

Previously the linkgraph was rebuilt before the viewport extents were finalized.

Revert 479f13fc41, Fix #7133, Fix #7136: "Codechange: Tweak ViewportAddLandscape so it no more relies on "go down as fast as possible" tile height model (Patch by adf88, #6583)"

This reverts commit 479f13fc4133f2970aff82d2d0fb9b3c0cb919da.

Fix: Some code and comment typos

Found with codespell

Revert: Sprite sorting optimisation sorted incorrectly.

This reverts commit 25ab9c1997f770f4a8a66bb3ad4b82ba87e3a977.

Codechange: Improve (un)zoom performance

When zooming out with a high res display, there can be about 150k sprites
to be sorted before displaying. With the O(n^2) complexity of the sprite
sorter, this can take several seconds.

This patch works around this by sorting the sprites by the xmin coordinate
first using QSort, which later allows an early bailout out of the inner
loop. This is enough to cut down the full unzoom time on a 4k display to a
fraction of second.

Feature: Framerate display window (#6822)

Frame rate and various game loop/graphics timing measurements and graphs. Accessible via the Help menu, and can print some stats in the console via the fps command.