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 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().

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: Add unit-test to check if nested widget parts of properly closed.

Properly closed means exactly one EndContainer for every Container widget.

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.

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: use better location for the "invalid" action sentinel value

It used to be a random sentinel for end-of-(widget-)list that was used to tell
that no action has taken place yet. Since the last action is practically the
widget that was pressed, add the sentinel to that enumeration.

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

Fix dec7ff6b0c: Dropdowns couldn't be closed by pressing the parent button. (#10954)

Since dropdowns self-close, the detection of re-clicking a dropdown
button no longer worked, as the dropdown is already closed.

Instead set (and then test) a flag on the parent widget to indicate that
the dropdown closed. This method avoids looping windows on every click.

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.

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.

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.

Add: Define scaled WidgetDimensions.

Includes RectPadding container.

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.

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

Similar code is already repeated in other locations.

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: Use override specifer for overriding member declarations

This is a C++11 feature that allows the compiler to check that a virtual
member declaration overrides a base-class member with the same signature.

Also src/blitter/32bpp_anim_sse4.hpp +38 is no longer erroneously marked
as virtual despite being a template.

(svn r27900) -Change [FS#6568]: Remove the gap between windows when positioning them after opening.
-Fix: Make automatic window-positioning RTL-aware.
-Fix: Automatic window-positioning now uses GUI-scale/style dependent sizes/distances instead of fixed pixel values.