Codechange: Remove direct access to _colour_gradient.

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

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: Add GetParentWidget() to widgets.

This allows to get parent widgets in the nested tree from bottom-up.

Codechange: Make widget index const to prevent changes. (#11658)

This guards against future widget index manipulation.

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.

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: Rename nested array to widget lookup.

This changes from naming storage-type to naming functionality.

* `FillNestedArray` is renamed to `FillWidgetLookup`.
* `Window::nested_array` is renamed to `Window::widget_lookup`.
* `array` parameter renamed as well.

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`.

Change: Hide bevel for resizeable sparse layout windows. (#11572)

When clicked, the button is still highlighted to show that it is active.

The bevel is controlled with widget_data by RWV_SHOW_BEVEL or RWV_HIDE_BEVEL values.

Codechange: Add specific WidgetDimension for dropdown list window. (#11554)

This avoids contorting fullbevel dimensions.

Codechange: Vertical spacing for caption is captiontext, not framerect. (#11550)

This does not really matter as the caption height is sized correctly later anyway, so this just avoids confusion.

Change: Revert pressed-button content shifting introduced in r2161.

This restores original behaviour, and prevents all image buttons being slightly too large.

Codechange: Make a generic DrawRectOutline function from DrawOutline. (#11524)

This allows drawing an outline from Rect, not just constrained to a Widget's Rect. And reduces duplication a little.

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 method to guess the width/height required for a multiline string.

This is necessary for widget layouts where a minimum width is not yet known during UpdateWidgetSize().

Fix: Extra space allocated to container-within-container may not get allocated to children. (#11471)

Always derive additional length from contained widgets instead of from the container, as the container's minimal length may have been adjusted by an NC_EQUALSIZE parent container.

Add: WidgetDimensions for 'sparse' widget windows.

These are for windows that have space between widgets instead of being clumped together.

Codechange: Skip invisible (zero-size) widgets in PIP Containers.

This gets rid of doubled-up spacing where an invisible child widget would be.

Codechange: Add ability to allocate PIP-space dynamically by ratio.

This can be used to space out, centre, start-align, or end-align widgets without additional spacers.

Codechange: Don't be lenient with invalid NWidgetPart lists.

Some NWidgetPart combinations were ignored but it was not clear that they do nothing. Instead, assert if NWidgetPart is incorrectly applied.

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.

Add: Debug tool to draw widget outlines. (#11401)

This is considered a developer tool and is controlled from the help menu (or default hotkey Ctrl-O).

This draws a white dashed outline around widgets. NWidgetSpacer and (unused) WWT_EMPTY widgets are also filled with check pattern to highlight them, as they usually indicate a design issue.

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.

Codechange: Return update nwid_begin instead of count.

This avoids needing to keep track of how many widget parts have been consumed, instead we only to ensure nwid_begin < nwid_end.

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

Change: Allow text shadow on WWT_EMPTY/WWT_TEXT to extend horizontally. (#11065)

This alleviates text shadows of truetype fonts being cropped in some
window layouts.

Fix #10811: Crash getting row from non-resizable widget. (#10833)

GetScrolled*FromWidget took line height from the widget's resize_y value,
however not all widgets are resizable, resulting in a division-by-zero.

Allow passing line height explicitly in cases where a widget is not
resizable.

Feature: opt-in survey when exiting a game

On first start-up, the game will ask if you want to participate
in our automated survey. You have to opt-in, and can easily opt-out
(via the Options) at any time.

When opt-in, whenever you exit a game, a JSON blob will be send
to the survey server hosted by OpenTTD. This JSON blob contains
information that gives a global picture of the game just played:
- What settings were used
- How many humans vs AIs
- How long the game has been played
- Basic information about the OS / CPU

All this information is kept very generic, so there is no
chance we send private information to our survey server.
Nothing in the JSON blob could identify you as a person; it
mostly tells about the game played. At any time you can see
what the JSON blob includes, by pressing the "Preview Survey
Results" button in-game.

Cleanup: widget pos_x/y are already int. (#10809)

Remove old casts left over from when pos_x/y were unsigned.

Fix: WWT_TEXT with SetTextStyle did not work. (#10797)

FontSize was passed to incorrect parameter of DrawString function.

Change: Rename text colour NWidgetPart to SetTextStyle and add font size.

This allows to set both text colour and size for any widget with default
drawing.

Add: Helper to update widget vertical size.

This avoids directly setting min_y outside widget code.

Codechange: Reorder and properly declare DrawSpriteIgnorePadding().

Parameters have been rearranged to be closer to those of the standard
DrawSprite() function, and PaletteID can now be set.

Change: Standardize progress bar layout.

Progress bars are drawn differently depending on when it was added, with
different layouts and sizes.

This change adds a standard padding size to use, and makes all progress
bars visually similar, with scaled padding.

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: Split vscroll and hscroll padding.

Vertical and horizontal scrollbars are different sizes, this allows
different padding for each type.

Add: Define scaled WidgetDimensions.

Includes RectPadding container.

Change: Set up suggested widget padding for panel, frame and inset.

Window handlers are free to ignore the suggested padding, however some
handlers have logic that assumes this information was already provided.

Fix: Ensure 31-bit shifts are unsigned. (#10128)

Shifting a signed 32-bit integer by 31 bits is undefined behaviour.
A few more than necessary are switched to unsigned for consistentency.

Change: Add flag to apply resize to largest resize step first.

Resize step is normally allocated equally amongst all resizable widgets.
With this flag, we allocate as much as possible from the largest
resize step first.

Change: Default widget text colour to black.

TC_FROMSTRING really means blue, and we almost never actually use
blue text.

Codechange: use "[[maybe_unused]]" instead of a wide variety of other ways we had

While at it, replace OTTD_ASSERT with WITH_ASSERT, as this
is always set if assert() is valid. No matter if NDEBUG is set
or not.

Fix: Apply unscaled padding to Viewport inside WWT_INSET. (#9219)

Since pixel dimensions in SetPadding() are scaled by GUI size, padding for inset viewports was excessive.

Instead, automatically apply padding for WWT_INSET at widget level. This applies to all widgets inside a WWT_INSET, which in all instances is a NWID_VIEWPORT.

Codechange: Make GetCurrentRect() conform to usual Rect bounds, and reuse it.

Similar code is already repeated in other locations.

Fix: Crash when extra viewport height is zero with sign in view. (#9175)

If a viewport sign straddles the top of a viewport, a crash will occur if the viewport height is zero. This is resolved by simply not attempting to draw the viewport in this situation, consistent with other widgets.

Cleanup: Remove unnecessary parameter of GetScrolledRowFromWidget()

Line height defaults to the resize height of the relevant widget, which is
set in all cases. Therefore it is not necessary to specify this value every time.

Additionally fixes scrolled padding for the framerate window.

Codechange: Spell 'Viewport' consistently

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