Codechange: Make all NWidgetPart arrays constexpr.

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

Fix #11655: Crash due to NWidgetMatrix modifying widget->index. (#11657)

NWidgetMatrix modifies its child widget's index to indicate which element
is to be drawn, which now causes issues with code that does not know about
stuffing extra data into the index.

Instead, let NWidgetMatrix store the currently processing element, and
retrieve this information from the matrix widget while child widgets are
being drawn.

This means only widgets that are children of NWidgetMatrix need to know
anything about their extra data.

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: Draw unavailable mask over picker sprite instead of behind it.

This makes these disabled picker buttons consistent with other disabled buttons.

Codechange: Add Rect version of FillDrawPixelInfo().

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

Codechange: Optionally allow passing state to GUIList sorter function.

GUIList sorter functions can currently only use global state, which makes per-window-instance sorting difficult.

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: Remove now-unnecessary containers in picker layouts. (#11473)

These are no longer necessary as the issue they work around was resolved by #11471

Cleanup: Remove some unused functions. (#11429)

These were picked up with cppcheck.

Codechange: Add __FILE__/__LINE__ of WindowDesc to WindowDesc.

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

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: Reorganise hotkey initialisation. (#10951)

Hotkeys are now initialized inline, and use std::vector instead of
separate static C-arrays and std::string instead of char *. The list end
marker is no longer required.

Fix: Don't use a loop to test if classid is valid. (#10818)

Additionally the Object class test was broken.

Codechange: Use GetScrolled(Row/Item)FromWidget in more places.

In many instances the clicked row position is 'manually' calculated
instead of using the GetScrolledRowFromWidget helper function, with
variations on checks. Replace with the two helpers where possible.

Codechange: Scrollbar methods now accept size_t.

This clears up a lot of casts from size_t to int.

Fix: Don't double-pad existing size when adding widget padding.

UpdateWidgetSize's size parameter already includes padding.

Fix #10335: Set initial scrollbar count for object GUI. (#10336)

This previously happened when the window was resized by itself which was fixed by #10196. Explicitly set the count instead.

Fix #10021: Object GUI resized when switching between different objects. (#10196)

* Fix: Scale object gui margin by interface scale.

* Fix: Improve padding on object info text.

* Fix #10021: Resizing for 1/2/4 object views didn't account for interface scale.

As halving and doubling padding is problematic due to rounding, it is now
added on lower view counts instead of removing on higher view counts.

Change: Use power-of-2 scaling for some dimensions in GUI.

These are related to drawing sprites that are normally drawn on the
landscape, and should therefore still follow power-of-2 scaling to fit
correctly.

Change: Use Rect helpers for widget drawing.

This replaces repetitive and sometimes unwieldy use of constants.

Codechange: Template DoCommandP to automagically reflect the parameters of the command proc.

When finished, this will allow each command handler to take individually
different parameters, obliviating the need for bit-packing.

Cleanup: nested_array should not be accessed directly.

Replace accesses with GetWidget() as documented.

Fix: adjust object and rail station selection window padding to be consistent (#8929)

consistent