Codefix: DrawEngineList does not accept EngineID.

Replace min/max parameters of DrawEngineList with scrollbar reference, and use iterators instead of indices.

Codechange: Remove direct access to _colour_gradient.

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

Fix b7630b0: Incorrect padding for text purchase list. (#12160)

Restore to original (and more normal) framerect padding.

Change: Decouple and remove landscape-dependent cargo types. (#11719)

Cargo types of default engines, industries and houses are now specified in terms of label.

Codechange: Make all NWidgetPart arrays constexpr.

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

Codechange: Redefine some cargo-related values in terms of CargoID instead of CargoType.

Values used as special filter types are now defined as offsets from NUM_CARGO instead of confusingly reusing CARGO_NO_REFIT/CARGO_AUTO_REFIT types.

Codechange: Split CT_INVALID into CT_INVALID and INVALID_CARGO.

INVALID_CARGO is a CargoID and should be used for most purposes in game.
CT_INVALID is a CargoType used for defining default properties.

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.

Feature: Place cargo icon on cargo filter dropdowns.

Reveal the pixel art.

Fix 7cfcf65: Check if last-remembered build vehicle cargo filter is valid. (#11486)

This can be invalid when switching between games with different cargoes loaded.

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: Simplify cargo filter lists, building only when required.

Some cargo filter lists were built in advance, and used as lookups to test which cargo type to filter.

Instead, use the Cargo ID directly as the filter parameter, and build the lists only when the drop down list is used.

Codechange: Add base() method to StrongType to allow access to the base type without casting. (#11445)

This removes the ability to explicitly cast to the base type, but the requirement
to use .base() means the conversion is still explicit.

Codechange: Add __FILE__/__LINE__ of WindowDesc to WindowDesc.

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

Fix: Check for engine variant loops during NewGRF initialization. (#11343)

Invalid NewGRFs could set up an engine variant loop that never ends. This
was checked for in some places that evaluated variants, but not all. In
most cases this would result in the engines not appearing, but could
potentially cause an infinite loop and crash.

Instead, during NewGRF initialization detect loops and remove invalid
variants before setting display flags.

Codechange: Don't pass GUI cargo filter constants to command system. (#11320)

CMD_BUILD_VEHICLE expects CT_INVALID to indicate a new vehicle should not
be refitted on build, but the code passed CF_NONE instead. CF_NONE has the
same numeric value at CT_INVALID, so the test passed, but...

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: make explicit when a TileIndex is cast to its basetype (#11190)

This prevents people accidentially assigning a TileIndex to a Date
or any other type they shouldn't.

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.

Codechange: Use IsValidCargoID/IsValidCargoType.

IsValidCargoType() is used only for unmapped IDs.

Codechange: Pass reference instead of pointer to GUI*Lists. (#10822)

Pointer-avoidance.

Codechange: Add and use GetScrolledItemFromWidget to get a list item.

This function returns an iterator, either to the selected item or the
container's end.

This makes handling the result more robust as indices are not used.

Codechange: Scrollbar methods now accept size_t.

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

Fix: Set TC_NO_SHADE only for shaded engine in purchase list.

Additionally use TC_FORCE to prevent additional colours in the shaded text.

Feature: Separate rail/road and sea/air velocity units, and add knots. (#10594)

This is achieved by packing vehicle type along with the velocity so that
the string system can decode and pick the appropriate unit.

Codechange: add non-nullptr asserts in cases where it should never be nullptr

Though where similar calls are checked for nullptr as in those instances of
the use of that function it can actually return nullptr. In other words, write
down the assumption that the function never returns nullptr in an assert.

Fix #10032: Capacities of articulated vehicles in build window

See also: #9954

Fix #10220: Adding unavailable variants failed for non-rail engines. (#10297)

Unavailable parent variant engine for non-rail engines was added to the
wrong (temporary) list so the hierarchy was not added correctly.

Feature: Vehicle add-ons can now group engines in purchase list.

Grouped engines are collapsed by default but can be expanded. This allows
similar engines to be grouped together to avoid cluttering the list.

Suggested uses for this are e.g.:
* Liveries; same stats but different paint job.
* Re-gearing; engine design is mostly the same but different stats.

... but avoiding complex hidden cargo subtype refit systems.

Grouped engines are otherwise separate, so can be independently
autoreplaced, even between variants.

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.

Codechange: Template DoCommand 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.

Codechange: Make TileIndex a "strong" typedef to give it a distinct type.

This is accomplished by changing it to a single member struct with the
appropriate operator overloads to make it all work with not too much
source modifications.

Fix: Count engine details text in lines rather than pixels. (#9107)

This allows the details panel to scale correctly for different zoom levels.

Fix: Violation of strict weak ordering in engine name sorter

This could be caused by an engine being renamed, and the old
name being cached from a previous sort.

See: #7838

Fix #7594: Max speed rendered incorrectly in road vehicle purchase window when using original acceleration model (#7597)

An incorrect DParam index was used.