(svn r7635) -Fix (r7618, r7621): Guard against recursive deletion. It is possible that when a
parent window is deleted it deletes its child (always) and in turn, through some
code the child initiates the deletion of the parent which, if not guarded
against, deletes the child and so on...

(svn r7619) -Feature (Internal): Add support for modal children. It's a window-child that
will block activity for the parent window until the modal popup is dismissed.

(svn r7618) -Feature: Add support for a parent<>child relationship in Window terms. A child
is a window whose parent pointer is non-null. Deleting the parent cascades deleting
the children as well; children first.

(svn r7616) -Cleanup:
-(re)set _rename_[id/what] to -1 to catch invalid calls (main_gui.c)
-Only invalidate widget of pause/ff instead of whole window (main_gui.c)
-Remove numbering from WE_ and WC_ as it's not needed, also remove
non-existing windowclasses (window.h, openttd.h)
-Give names to some of the enums (window.h)
-In UninitWindowSystem not only free malloc'd widgets, but also reset the z-array (window.c)
-Some coding style, comments, etc.

(svn r7565) -Codechange: Rework DEBUG functionality. Look for appropiate debugging levels to
use in debug.h. grfmsg() is now used as a specific debug-function for grf.

(svn r7409) -Codechange: Make the ResizeWindow function also available outside of window.c. This makes
it possible to programmatically resize windows specifying a delta x,y.

(svn r7356) -Codechange: replace 'for (i = 0, wi = w->widget; wi->type != WWT_LAST; i++, wi++)' type for loops with 'for (i = 0; i < w->window_count; i++) { wi = &w->widget[i];'-type for loops for better readability.
-Codechange: use IsWindowWidget(Disabled|Hidden) in favor of IsWidget(Disabled|Hidden).

(svn r7352) -Codechange: add widget_count parameter to the window.
-Codechange: check whether widget indices are valid for all the (Set|Is)WindowWidget(Disabled|Lowered|Hidden) and related functions.

(svn r7313) -Codechange: Calling invalidate data on a window will surely warrant a redraw, so call
that after the WE_INVALIDATE_DATA event and remove (some of) the superflouous calls.

(svn r7205) -Fix [FS#350, SF#1560913]: Window allocation and deletion messed with the actual window
structs inside their array, and possibly invalidating pointers higher up.
Meaning that any function called within an wndproc could cause unknown/invalid pointers
once control was returned to this function. Solved by the introduction of an extra
abstraction layer, an array of z-window positions that is only concerned with the
pointers.

(svn r7202) -Codechange: Move _viewports and _active_viewports local to viewport.c and have them
called from the appropiate places in window.c

(svn r7200) -Codechange: remove unneeded redraw (console.c), coding style, use FindWindowById
instead of _windows loop (viewport.c), remove dump-code (mixer.c), MSVC6 borkdness
in stdafx.h, constness (viewport.c), variable localization (win32.c), comments (window.c)

(svn r7157) -Fix [FS#221, SF1168820]: Some mouse events possibly lost under high CPU load, handle
mouse input right away instead of waiting for GameLoop. (KUDr)

(svn r7156) -Codechange: Remove obsolete variable, localize global variable, use GB and change logic
of the win32: TAB speeds up, but ALT+TAB doesn't code.

(svn r7153) -Fix [FS#279]: Some keyboard events possibly lost under high CPU load, handle
keyboard input in place instead of global variables magic. (KUDr)

(svn r7138) -Fix: [vehicle list windows] fixed a rare crash where having some (not all) vehicle list windows open for a player, that goes bankrupt would crash the game
-Codechange: closing all windows for a player will now loop all windows and close those, which got the player as caption instead of having a list of windows to close

(svn r7130) -Codechange: Handle the positioning of windows through the desc->left/top settings with
some special values (WDP_) instead of checking window-class. This also fixes FS#172
now that we can position windows arbitrarily and are not restricted to window-classes.

(svn r7092) -Codechange: Add function to send a window message to a whole class of windows,
SendWindowMessageClass().

(svn r6961) -Codechange: Remove relic from r212 WWT_NODISTXTBTN which was originally used to not
to allow clicking if a button was disabled. This has been superseded in r212 with
general code that doesn't allow any click events for disabled buttons.

(svn r6925) -Codechange: Be more strict with widget distinctions. WWT_PANEL is only plain panel,
WWT_IMGBTN must contain an image for drawing. Renamed WWT_PANEL_2 to WWT_IMGBTN_2
because that is what it is. Added WWT_PUSHBTN that is either just a pushable button,
or a textbutton, which text's drawn dynamically independent of widget.

(svn r6661) Feature: Windows are not restricted to 32 widget items anymore.
The functions required to do so are to be found in window.h.
Rather then use the old deprecated disabled_state, hidden_state and click_state uint32 variables,
we now need to use accessors like SetWindowWidgetDisabledState, SetWindowWidgetHiddenState or SetWindowWidgetLoweredState.
This is the final commit for the merge of XTDwidget branch.

(svn r6651) -Coding feature: added the windowevent WE_INVALIDATE_DATA
This gives the ability to invalidate some window data and recalculate as needed instead of doing it for each WE_PAINT

This event is called right away when using InvalidateWindowData(), so it may be a good idea to set a bool or similar in the window
or similar and then act on that bool in WE_PAINT instead of doing a lot of stuff in WE_INVALIDATE_DATA as it might be called more than once before WE_PAINT is called

InvalidateWindowData() will not automatically repaint the window, so if you want to repaint it as well, you need to mark it dirty as well.

Made the depot windows use WE_INVALIDATE_DATA to set when to generate the engine and wagon lists instead of at each redraw
It makes no sense to regenerate the list when say using the scrollbar if we know that no vehicle have entered or left the list

NOTE: currently there is a piece of code to generate the list when it's not needed and compare it to the stored list and assert if they mismatch
This check is somewhat slow and kills the whole idea of WE_INVALIDATE_DATA, so it's a short lived one to verify that InvalidateWindowData() is used everywhere where it's needed

(svn r6631) -Codechange: Use accessors for click_state.
Another step toward merging XTDwidget.
The only two files not converted (window.h and widget.c) will be done at the very last commit)

(svn r6381) -Cleanup: make the '/* */' comments that span multiple lines more uniform.
-Cleanup: whitespace alignment of a few tables.

(svn r6345) -Codechange: AllocateWindowDescFront() now ensures that window_number is set before calling the WE_CREATE event
this allows using the window_number in WE_CREATE window event handlers

(svn r6038) -Codechange: move mousewheel code to event WE_MOUSEWHEEL instead of a general function that handles that
-Codechange: use always 'e' for WindowsEvent, neverr 'we'

(svn r5946) -Add: merged the TGP branch to mainline. TGP adds:
- New optional landscape generator (TerraGenesis Perlin)
- Load heightmaps (either BMP or PNG)
- Progress dialog while generating worlds (no longer a 'hanging' screen)
- New dialogs for NewGame, Create Scenario and Play Heightmap
- Easier to configure your landscape
- More things to configure (tree-placer, ..)
- Speedup of world generation
- New console command 'restart': restart the map EXACTLY as it was when you
first started it (needs a game made after or with this commit)
- New console command 'getseed': get the seed of your map and share it with
others (of course only works with generated maps)
- Many new, world generation related, things
- Many internal cleanups and rewrites
Many tnx to those people who helped making this:
Belugas, DaleStan, glx, KUDr, RichK67, Rubidium, and TrueLight (alfabetic)
Many tnx to those who helped testing:
Arnau, Bjarni, and tokai (alfabetic)
And to all other people who helped testing and sending comments / bugs
Stats: 673 lines changed, 3534 new lines, 79 new strings

(svn r3564) Several smaller changes:
- Don't treat non-booleans as booleans
- Reduce variable scope
- Bracing
- Use DeMorgan's law to make conditionals easier to read
- if cascade -> switch
- Replace some magic numbers by symbolic names
- Avoid assignments within other statements

(svn r3247) - Fix: "[ 1335580 ] sticky windows not sticky anymore"
Determine clicked status of sticky icon from window flags rather than the widget click state. This keeps the status in one place where it can't get out of sync.

(svn r3181) -Bracing
-Indentation
-Whitespace
-DeMorgan's Law
-Test with NULL or 0 for non-booleans
-'\0' instead of 0 for chars
-Remove redundantly redundant comments (like DoFoo(); // Do foo)
-Join multiple short lines with a single statement
-Split single lines with multiple statements
-Avoid assignments in if

(svn r3173) Use the trinary operator and switch to improve readability
Also align short cases nicely

(svn r3133) - static, const
- remove long unused stuff and bogus comments
- complement struct typedefs
- remove read-only (_demo_mode) and unused (_fix_mouse_at) global variables

(svn r3078) Some more stuff, which piled up:
- const, whitespace, indentation, bracing, GB/SB, pointless casts
- use the trinary operator where appropriate
- data types (uint[] -> AcceptedCargo, ...)
- if cascade -> switch
- if (ptr) -> if (ptr != NULL)
- DeMorgan's Law
- Fix some comments
- 0 -> '\0', change magic numbers to symbolic constants

(svn r2962) - const correctness for all Get* functions and most Draw* functions that don't change their pointer parameters
- change a lot of byte player types to PlayerID
- beautify header files, same "#endif /* filename */" ending

(svn r2161) - Fix: When resizing a window, the button is also visibly depressed
- CodeChange: Use images as arrows in the scenario-date scroller, looks better
- Feature: Clicked buttons with images/text now visibly depress their contents when pressed (eg it really seems like the button is moving)
- Fix: Fix sprite offsets of the arrow sprites in openttd.grf

(svn r2152) - Fix: Chatbar in MP games is now on-top of the news window.
- CodeChange: Introduction of SendWindowMessage() where a window can send another window a message (ala windows style msg, wparam, lparam). Messages can be sent by windowclass and by windowpointer.
- CodeChange: IsVitalWindow() simplifies a lot of checks for window handling that need to know what windows it can close, or be on top of, etc.

(svn r1497) -Fix: [1101179] Crash if generating land while industry window is open. This also happened for towns and the land information window
-Added DeleteWindowByClass() function that deletes all windows of a given class

(svn r1479) -Added highscore chart (accessible from the difficulty window) with top5 companies for a given difficulty (select the difficulty in the menu)
-Added endgame score on 1 jan 2051 where you are added to the highscore if sufficiently large points have been accumulated. Game is paused while
-These values are saved in hs.dat; added read/write functions for it
-Added code to delete all windows to show charts. There is one issue left: somehow a news-gui pops up in front of the the chart at the end of the game.

(svn r1478) -Fix: [1099195] mouse-wheel in train replace window. Scrollbar1 and Scrollbar2 now work independently. You can only scroll on list and scrollbar itself; scrollbar must be next widget of the list.
-Fix: updated the few gui's that didn't have the scrollbar right after the listbox.

(svn r1348) -Feature: resizable windows. Read the comment in window.h to find out
how the system works. All useful windows are already made resizable. Enjoy :)
-Fix: fixed some GUI-glitches and flaws along the way