Codechange: Remove direct access to _colour_gradient.

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

Codechange: allow certain enumeration to be added

Otherwise C++20 doesn't like it.

Codechange: Make all NWidgetPart arrays constexpr.

This ensures that the arrays are not created at runtime and prevents using non-constexpr values.

Codechange: Use vector/unique_ptr inside widget containers.

This replaces a C-style double-linked-list which required all widgets
to have next/prev pointers, and removes the need for manual pointer management.

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.

Codechange: Use std::map to provide indexed widget access.

This removes the need to determine the biggest widget index and replaces C-style memory handling.

Codechange: Remove deferred nested_array initialization path. (#11640)

Having two ways (`FillNestedArray` and `SetupSmallestSize`) to initialize
`Window::nested_array` introduces confusion.

Instead, make `FillNestedArray` the canonical way, always call it, and remove
init_array from `SetupSmallestSize`.

Codechange: Add Rect version of FillDrawPixelInfo().

This simplifies most callers as they longer have to split out a rect.

Fix: Restore original cargo legend 'blob' dimensions. (#11480)

An off-by-one in a previous life made the 'blob' too narrow.

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: Add __FILE__/__LINE__ of WindowDesc to WindowDesc.

This is to allow unit-tests to produce more useful output.

Codechange: Move includes to correct place.

Some other source file inadvertently included things via smallmap_gui.h

Revert 6b68956: Move declaration of SmallMapWindow out of header file.

This split needlessly complicates `SmallMapWindow` for the sake of one method (no longer) used by `LinkGraphOverlay`.

Codechange: Assign/StoreSizePosition x/y can be negative. (#11416)

AssignSizePosition is used with negative values when an NWidgetMatrix is
scrolled, but they were passed as unsigned and then stored as signed.

Widget pos_x/pos_y were already made signed.

Fix: Incorrect padding for smallmap legend 'icon'.

The size of this icon is based off FONT_HEIGHT_SMALL - 1, so it makes sense to use a scaled 1 here.

Codechange: Use unified NWidgetContainer methods instead of duplicating.

Most NWidgetContainer derivatives implemented Draw() and GetWidgetFromPos()
the same way. Move this these to NWidgetContainer itself to avoid repeating.

Add: data parameter in Window::Close method.

This allows passing data when closing a window, e.g. to indicate how it was closed.

Codechange: Use begin/end of nwidget parts of begin/length.

This simplifies processing nwidget parts as, unlike the remaining length, the pointer to the end of the list never changes. This is the same principle as we use(d) for tracking end instead of length for C-style strings.

And this removes 160~ instances of the lengthof() macro.

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: migrate all Window-related timers to the new framework

This means we also say goodbye to GUITimers.

Codechange: introduce GetMainWindow() to properly account for nullptr checks

Some nullptr checks have been removed as they were not triggered with nullptr
with the null video driver and in dedicated server mode.

Feature: Variable GUI scale.

GUI scale is now variable from 100% to 500%, and no longer restricted to
powers-of-2.

Change: Use Rect helpers for widget drawing.

This replaces repetitive and sometimes unwieldy use of constants.

Change: Use CenterBounds function in more places.

CenterBounds may have a 1 pixel difference so the result is not exactly
the same.

Change: rename setting "max_heightlevel" to "map_height_limit"

This better reflects what it is, and hopefully removes a bit of
the confusion people are having what this setting actually does.

Additionally, update the text on the setting to better inform
users what it is doing exactly, so they can make an educated
decision on how to change it.

Next commit will introduce an "auto" value, which should be the
new default. The rename has as added benefit that everyone will
start out on the "auto" value.

Codechange: Spell 'Viewport' consistently

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

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

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

Change: Make mini-map widget capture mouse when left-click dragging.

This allows the mini-map to be dragged when the cursor has left the widget.