/* $Id: osk_gui.cpp 16516 2009-06-04 14:07:05Z alberth $ */

/** @file osk_gui.cpp The On Screen Keyboard GUI */

#include "stdafx.h"
#include "string_func.h"
#include "strings_func.h"
#include "debug.h"
#include "window_func.h"
#include "gfx_func.h"
#include "querystring_gui.h"

#include "table/sprites.h"
#include "table/strings.h"

/** Widget numbers of the on-screen keyboard (OSK) window. */
enum OskWidgets {
	OSK_WIDGET_CAPTION,         ///< Title bar.
	OSK_WIDGET_TEXT_BACKGROUND, ///< Background around the edit box.
	OSK_WIDGET_TEXT,            ///< Edit box.
	OSK_WIDGET_KEYS_BACKGROUND, ///< Background of the keys.
	OSK_WIDGET_CANCEL,          ///< Cancel key.
	OSK_WIDGET_OK,              ///< Ok key.
	OSK_WIDGET_BACKSPACE,       ///< Backspace key.
	OSK_WIDGET_SPECIAL,         ///< Special key (at keyborads often used for tab key).
	OSK_WIDGET_CAPS,            ///< Capslock key.
	OSK_WIDGET_SHIFT,           ///< Shift(lock) key.
	OSK_WIDGET_SPACE,           ///< Space bar.
	OSK_WIDGET_LEFT,            ///< Cursor left key.
	OSK_WIDGET_RIGHT,           ///< Cursor right key.
	OSK_WIDGET_LETTERS,         ///< First widget of the 'normal' keys.

	OSK_WIDGET_NUMBERS_FIRST = OSK_WIDGET_LETTERS,           ///< First widget of the numbers row.
	OSK_WIDGET_NUMBERS_LAST = OSK_WIDGET_NUMBERS_FIRST + 13, ///< Last widget of the numbers row.

	OSK_WIDGET_QWERTY_FIRST,                                 ///< First widget of the qwerty row.
	OSK_WIDGET_QWERTY_LAST = OSK_WIDGET_QWERTY_FIRST + 11,   ///< Last widget of the qwerty row.

	OSK_WIDGET_ASDFG_FIRST,                                  ///< First widget of the asdfg row.
	OSK_WIDGET_ASDFG_LAST = OSK_WIDGET_ASDFG_FIRST + 11,     ///< Last widget of the asdfg row.

	OSK_WIDGET_ZXCVB_FIRST,                                  ///< First widget of the zxcvb row.
	OSK_WIDGET_ZXCVB_LAST = OSK_WIDGET_ZXCVB_FIRST + 11,     ///< Last widget of the zxcvb row.
};

char _keyboard_opt[2][OSK_KEYBOARD_ENTRIES * 4 + 1];
static WChar _keyboard[2][OSK_KEYBOARD_ENTRIES];

enum {
	KEYS_NONE,
	KEYS_SHIFT,
	KEYS_CAPS
};
static byte _keystate = KEYS_NONE;

struct OskWindow : public Window {
	StringID caption;      ///< the caption for this window.
	QueryString *qs;       ///< text-input
	int text_btn;          ///< widget number of parent's text field
	int ok_btn;            ///< widget number of parent's ok button (=0 when ok shouldn't be passed on)
	int cancel_btn;        ///< widget number of parent's cancel button (=0 when cancel shouldn't be passed on; text will be reverted to original)
	Textbuf *text;         ///< pointer to parent's textbuffer (to update caret position)
	char *orig_str_buf;    ///< Original string.

	OskWindow(const WindowDesc *desc, QueryStringBaseWindow *parent, int button, int cancel, int ok) : Window(desc)
	{
		this->parent = parent;
		assert(parent != NULL);

		this->caption = (parent->widget[button].data != STR_NULL) ? parent->widget[button].data : parent->caption;

		this->qs         = parent;
		this->text_btn   = button;
		this->cancel_btn = cancel;
		this->ok_btn     = ok;
		this->text       = &parent->text;

		/* make a copy in case we need to reset later */
		this->orig_str_buf = strdup(this->qs->text.buf);

		/* Not needed by default. */
		this->DisableWidget(OSK_WIDGET_SPECIAL);

		this->FindWindowPlacementAndResize(desc);
	}

	~OskWindow()
	{
		free(this->orig_str_buf);
	}

	/**
	 * Only show valid characters; do not show characters that would
	 * only insert a space when we have a spacebar to do that or
	 * characters that are not allowed to be entered.
	 */
	void ChangeOskDiabledState(bool shift)
	{
		for (uint i = 0; i < OSK_KEYBOARD_ENTRIES; i++) {
			this->SetWidgetDisabledState(OSK_WIDGET_LETTERS + i,
					!IsValidChar(_keyboard[shift][i], this->qs->afilter) || _keyboard[shift][i] == ' ');
		}
		this->SetWidgetDisabledState(OSK_WIDGET_SPACE, !IsValidChar(' ', this->qs->afilter));
	}

	virtual void OnPaint()
	{
		bool shift = HasBit(_keystate, KEYS_CAPS) ^ HasBit(_keystate, KEYS_SHIFT);

		this->LowerWidget(OSK_WIDGET_TEXT);
		this->SetWidgetLoweredState(OSK_WIDGET_SHIFT, HasBit(_keystate, KEYS_SHIFT));
		this->SetWidgetLoweredState(OSK_WIDGET_CAPS, HasBit(_keystate, KEYS_CAPS));

		this->ChangeOskDiabledState(shift);

		SetDParam(0, this->caption);
		this->DrawWidgets();

		for (uint i = 0; i < OSK_KEYBOARD_ENTRIES; i++) {
			DrawCharCentered(_keyboard[shift][i],
				this->widget[OSK_WIDGET_LETTERS + i].left + 8,
				this->widget[OSK_WIDGET_LETTERS + i].top + 3,
				TC_BLACK);
		}

		this->qs->DrawEditBox(this, OSK_WIDGET_TEXT);
	}

	virtual void OnClick(Point pt, int widget)
	{
		/* clicked a letter */
		if (widget >= OSK_WIDGET_LETTERS) {
			bool shift = HasBit(_keystate, KEYS_CAPS) ^ HasBit(_keystate, KEYS_SHIFT);

			WChar c = _keyboard[shift][widget - OSK_WIDGET_LETTERS];

			if (!IsValidChar(c, this->qs->afilter)) return;

			if (InsertTextBufferChar(&this->qs->text, c)) this->InvalidateParent();

			if (HasBit(_keystate, KEYS_SHIFT)) {
				ToggleBit(_keystate, KEYS_SHIFT);
				this->widget[OSK_WIDGET_SHIFT].colour = HasBit(_keystate, KEYS_SHIFT) ? COLOUR_WHITE : COLOUR_GREY;
				this->SetDirty();
			}
			return;
		}

		switch (widget) {
			case OSK_WIDGET_TEXT: {
				/* Find the edit box of the parent window and give focus to that */
				if (this->parent->widget != NULL) {
					const Widget *wi = this->parent->GetWidgetOfType(WWT_EDITBOX);
					if (wi != NULL) this->parent->focused_widget = wi;
				}
				if (this->parent->nested_root != NULL) {
					const NWidgetCore *nwid = dynamic_cast<const NWidgetCore *>(this->parent->nested_root->GetWidgetOfType(WWT_EDITBOX));
					if (nwid != NULL) this->parent->nested_focus = nwid;
				}

				/* Give focus to parent window */
				SetFocusedWindow(this->parent);

				break;
			}

			case OSK_WIDGET_BACKSPACE:
				if (DeleteTextBufferChar(&this->qs->text, WKC_BACKSPACE)) this->InvalidateParent();
				break;

			case OSK_WIDGET_SPECIAL:
				/*
				 * Anything device specific can go here.
				 * The button itself is hidden by default, and when you need it you
				 * can not hide it in the create event.
				 */
				break;

			case OSK_WIDGET_CAPS:
				ToggleBit(_keystate, KEYS_CAPS);
				this->SetDirty();
				break;

			case OSK_WIDGET_SHIFT:
				ToggleBit(_keystate, KEYS_SHIFT);
				this->SetDirty();
				break;

			case OSK_WIDGET_SPACE:
				if (InsertTextBufferChar(&this->qs->text, ' ')) this->InvalidateParent();
				break;

			case OSK_WIDGET_LEFT:
				if (MoveTextBufferPos(&this->qs->text, WKC_LEFT)) this->InvalidateParent();
				break;

			case OSK_WIDGET_RIGHT:
				if (MoveTextBufferPos(&this->qs->text, WKC_RIGHT)) this->InvalidateParent();
				break;

			case OSK_WIDGET_OK:
				if (this->qs->orig == NULL || strcmp(this->qs->text.buf, this->qs->orig) != 0) {
					/* pass information by simulating a button press on parent window */
					if (this->ok_btn != 0) {
						this->parent->OnClick(pt, this->ok_btn);
						/* Window gets deleted when the parent window removes itself. */
						return;
					}
				}
				delete this;
				break;

			case OSK_WIDGET_CANCEL:
				if (this->cancel_btn != 0) { // pass a cancel event to the parent window
					this->parent->OnClick(pt, this->cancel_btn);
					/* Window gets deleted when the parent window removes itself. */
					return;
				} else { // or reset to original string
					strcpy(qs->text.buf, this->orig_str_buf);
					UpdateTextBufferSize(&qs->text);
					MoveTextBufferPos(&qs->text, WKC_END);
					this->InvalidateParent();
					delete this;
				}
				break;
		}
	}

	void InvalidateParent()
	{
		QueryStringBaseWindow *w = dynamic_cast<QueryStringBaseWindow*>(this->parent);
		if (w != NULL) w->OnOSKInput(this->text_btn);

		this->InvalidateWidget(OSK_WIDGET_TEXT);
		if (this->parent != NULL) this->parent->InvalidateWidget(this->text_btn);
	}

	virtual void OnMouseLoop()
	{
		this->qs->HandleEditBox(this, OSK_WIDGET_TEXT);
		/* make the caret of the parent window also blink */
		this->parent->InvalidateWidget(this->text_btn);
	}

	virtual void OnInvalidateData(int)
	{
		this->InvalidateWidget(OSK_WIDGET_TEXT);
	}
};

static const Widget _osk_widgets[] = {
{    WWT_CAPTION, RESIZE_NONE,  COLOUR_GREY,     0,   255,     0,    13, STR_QUERY_CAPTION, STR_NULL}, // OSK_WIDGET_CAPTION
{      WWT_PANEL, RESIZE_NONE,  COLOUR_GREY,     0,   255,    14,    29, 0x0,               STR_NULL}, // OSK_WIDGET_TEXT_BACKGROUND
{    WWT_EDITBOX, RESIZE_NONE,  COLOUR_GREY,     2,   253,    16,    27, 0x0,               STR_NULL}, // OSK_WIDGET_TEXT

{      WWT_PANEL, RESIZE_NONE,  COLOUR_GREY,     0,   255,    30,   139, 0x0,               STR_NULL}, // OSK_WIDGET_KEYS_BACKGROUND

{    WWT_TEXTBTN, RESIZE_NONE,  COLOUR_GREY,     3,   108,    35,    46, STR_QUERY_CANCEL,  STR_NULL}, // OSK_WIDGET_CANCEL
{    WWT_TEXTBTN, RESIZE_NONE,  COLOUR_GREY,   111,   216,    35,    46, STR_QUERY_OK,      STR_NULL}, // OSK_WIDGET_OK
{ WWT_PUSHIMGBTN, RESIZE_NONE,  COLOUR_GREY,   219,   252,    35,    46, SPR_OSK_BACKSPACE, STR_NULL}, // OSK_WIDGET_BACKSPACE

{ WWT_PUSHIMGBTN, RESIZE_NONE,  COLOUR_GREY,     3,    27,    67,    82, SPR_OSK_SPECIAL,   STR_NULL}, // OSK_WIDGET_SPECIAL
{     WWT_IMGBTN, RESIZE_NONE,  COLOUR_GREY,     3,    36,    85,   100, SPR_OSK_CAPS,      STR_NULL}, // OSK_WIDGET_CAPS
{     WWT_IMGBTN, RESIZE_NONE,  COLOUR_GREY,     3,    27,   103,   118, SPR_OSK_SHIFT,     STR_NULL}, // OSK_WIDGET_SHIFT

{ WWT_PUSHTXTBTN, RESIZE_NONE,  COLOUR_GREY,    75,   189,   121,   136, STR_EMPTY,         STR_NULL}, // OSK_WIDGET_SPACE

{ WWT_PUSHIMGBTN, RESIZE_NONE,  COLOUR_GREY,   219,   234,   121,   136, SPR_OSK_LEFT,      STR_NULL}, // OSK_WIDGET_LEFT
{ WWT_PUSHIMGBTN, RESIZE_NONE,  COLOUR_GREY,   237,   252,   121,   136, SPR_OSK_RIGHT,     STR_NULL}, // OSK_WIDGET_RIGHT

{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,     3,    18,    49,    64, 0x0,    STR_NULL},            // OSK_WIDGET_NUMBERS_FIRST = OSK_WIDGET_LETTERS
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    21,    36,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    39,    54,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    57,    72,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    75,    90,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    93,   108,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   111,   126,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   129,   144,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   147,   162,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   165,   180,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   183,   198,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   201,   216,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   219,   234,    49,    64, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   237,   252,    49,    64, 0x0,    STR_NULL},            // OSK_WIDGET_NUMBERS_LAST

{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    30,    45,    67,    82, 0x0,    STR_NULL},            // OSK_WIDGET_QWERTY_FIRST
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    48,    63,    67,    82, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    66,    81,    67,    82, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    84,    99,    67,    82, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   102,   117,    67,    82, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   120,   135,    67,    82, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   138,   153,    67,    82, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   156,   171,    67,    82, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   174,   189,    67,    82, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   192,   207,    67,    82, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   210,   225,    67,    82, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   228,   243,    67,    82, 0x0,    STR_NULL},            // OSK_WIDGET_QWERTY_LAST

{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    39,    54,    85,   100, 0x0,    STR_NULL},            // OSK_WIDGET_ASDFG_FIRST
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    57,    72,    85,   100, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    75,    90,    85,   100, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    93,   108,    85,   100, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   111,   126,    85,   100, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   129,   144,    85,   100, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   147,   162,    85,   100, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   165,   180,    85,   100, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   183,   198,    85,   100, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   201,   216,    85,   100, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   219,   234,    85,   100, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   237,   252,    85,   100, 0x0,    STR_NULL},            // OSK_WIDGET_ASDFG_LAST

{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    30,    45,   103,   118, 0x0,    STR_NULL},            // OSK_WIDGET_ZXCVB_FIRST
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    48,    63,   103,   118, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    66,    81,   103,   118, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,    84,    99,   103,   118, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   102,   117,   103,   118, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   120,   135,   103,   118, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   138,   153,   103,   118, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   156,   171,   103,   118, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   174,   189,   103,   118, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   192,   207,   103,   118, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   210,   225,   103,   118, 0x0,    STR_NULL},
{    WWT_PUSHBTN, RESIZE_NONE,  COLOUR_GREY,   228,   243,   103,   118, 0x0,    STR_NULL},            // OSK_WIDGET_ZXCVB_LAST

{   WIDGETS_END},
};

static const int HALF_KEY_WIDTH = 7;  // Width of 1/2 key in pixels.
static const int INTER_KEY_SPACE = 2; // Number of pixels between two keys.

/**
 * Add a key widget to a row of the keyboard.
 * @param hor     Row container to add key widget to.
 * @param height  Height of the key (all keys in a row should have equal height).
 * @param numhalf Number of 1/2 key widths that this key has.
 * @param widtype Widget type of the key. Must be either \c NWID_SPACER for an invisible key, or a \c WWT_* widget.
 * @param widnum  Widget number of the key.
 * @param widdata Data value of the key widget.
 * @note Key width is measured in 1/2 keys to allow for 1/2 key shifting between rows.
 */
static void AddKey(NWidgetHorizontal *hor, int height, int num_half, WidgetType widtype, int widnum, uint16 widdata)
{
	int key_width = HALF_KEY_WIDTH + (INTER_KEY_SPACE + HALF_KEY_WIDTH) * (num_half - 1);

	if (widtype == NWID_SPACER) {
		if (!hor->IsEmpty()) key_width += INTER_KEY_SPACE;
		NWidgetSpacer *spc = new NWidgetSpacer(key_width, height);
		hor->Add(spc);
	} else {
		if (!hor->IsEmpty()) {
			NWidgetSpacer *spc = new NWidgetSpacer(INTER_KEY_SPACE, height);
			hor->Add(spc);
		}
		NWidgetLeaf *leaf = new NWidgetLeaf(widtype, COLOUR_GREY, widnum, widdata, STR_NULL);
		leaf->SetMinimalSize(key_width, height);
		hor->Add(leaf);
	}
}

/** Construct the top row keys (cancel, ok, backspace). */
static NWidgetBase *MakeTopKeys()
{
	NWidgetHorizontal *hor = new NWidgetHorizontal;
	int key_height = 12;

	AddKey(hor, key_height, 6 * 2, WWT_TEXTBTN,    OSK_WIDGET_CANCEL,    STR_QUERY_CANCEL);
	AddKey(hor, key_height, 6 * 2, WWT_TEXTBTN,    OSK_WIDGET_OK,        STR_QUERY_OK);
	AddKey(hor, key_height, 2 * 2, WWT_PUSHIMGBTN, OSK_WIDGET_BACKSPACE, SPR_OSK_BACKSPACE);
	return hor;
}

/** Construct the row containing the digit keys. */
static NWidgetBase *MakeNumberKeys()
{
	NWidgetHorizontal *hor = new NWidgetHorizontal;
	int key_height = 16;

	for (int widnum = OSK_WIDGET_NUMBERS_FIRST; widnum <= OSK_WIDGET_NUMBERS_LAST; widnum++) {
		AddKey(hor, key_height, 2, WWT_PUSHBTN, widnum, 0x0);
	}
	return hor;
}

/** Construct the qwerty row keys. */
static NWidgetBase *MakeQwertyKeys()
{
	NWidgetHorizontal *hor = new NWidgetHorizontal;
	int key_height = 16;

	AddKey(hor, key_height, 3, WWT_PUSHIMGBTN, OSK_WIDGET_SPECIAL, SPR_OSK_SPECIAL);
	for (int widnum = OSK_WIDGET_QWERTY_FIRST; widnum <= OSK_WIDGET_QWERTY_LAST; widnum++) {
		AddKey(hor, key_height, 2, WWT_PUSHBTN, widnum, 0x0);
	}
	AddKey(hor, key_height, 1, NWID_SPACER, 0, 0);
	return hor;
}

/** Construct the asdfg row keys. */
static NWidgetBase *MakeAsdfgKeys()
{
	NWidgetHorizontal *hor = new NWidgetHorizontal;
	int key_height = 16;

	AddKey(hor, key_height, 4, WWT_IMGBTN, OSK_WIDGET_CAPS, SPR_OSK_CAPS);
	for (int widnum = OSK_WIDGET_ASDFG_FIRST; widnum <= OSK_WIDGET_ASDFG_LAST; widnum++) {
		AddKey(hor, key_height, 2, WWT_PUSHBTN, widnum, 0x0);
	}
	return hor;
}

/** Construct the zxcvb row keys. */
static NWidgetBase *MakeZxcvbKeys()
{
	NWidgetHorizontal *hor = new NWidgetHorizontal;
	int key_height = 16;

	AddKey(hor, key_height, 3, WWT_IMGBTN, OSK_WIDGET_SHIFT, SPR_OSK_SHIFT);
	for (int widnum = OSK_WIDGET_ZXCVB_FIRST; widnum <= OSK_WIDGET_ZXCVB_LAST; widnum++) {
		AddKey(hor, key_height, 2, WWT_PUSHBTN, widnum, 0x0);
	}
	AddKey(hor, key_height, 1, NWID_SPACER, 0, 0);
	return hor;
}

/** Construct the spacebar row keys. */
static NWidgetBase *MakeSpacebarKeys()
{
	NWidgetHorizontal *hor = new NWidgetHorizontal;
	int key_height = 16;

	AddKey(hor, key_height,  8, NWID_SPACER, 0, 0);
	AddKey(hor, key_height, 13, WWT_PUSHTXTBTN, OSK_WIDGET_SPACE, STR_EMPTY);
	AddKey(hor, key_height,  3, NWID_SPACER, 0, 0);
	AddKey(hor, key_height,  2, WWT_PUSHIMGBTN, OSK_WIDGET_LEFT,  SPR_OSK_LEFT);
	AddKey(hor, key_height,  2, WWT_PUSHIMGBTN, OSK_WIDGET_RIGHT, SPR_OSK_RIGHT);
	return hor;
}


static const NWidgetPart _nested_osk_widgets[] = {
	NWidget(WWT_CAPTION, COLOUR_GREY, OSK_WIDGET_CAPTION), SetDataTip(STR_QUERY_CAPTION, STR_NULL),
	NWidget(WWT_PANEL, COLOUR_GREY, OSK_WIDGET_TEXT_BACKGROUND),
		NWidget(WWT_EDITBOX, COLOUR_GREY, OSK_WIDGET_TEXT), SetMinimalSize(252, 12), SetPadding(2, 2, 2, 2),
	EndContainer(),
	NWidget(WWT_PANEL, COLOUR_GREY, OSK_WIDGET_KEYS_BACKGROUND), SetPIP(5, 2, 3),
		NWidgetFunction(MakeTopKeys), SetPadding(0, 3, 0, 3),
		NWidgetFunction(MakeNumberKeys), SetPadding(0, 3, 0, 3),
		NWidgetFunction(MakeQwertyKeys), SetPadding(0, 3, 0, 3),
		NWidgetFunction(MakeAsdfgKeys), SetPadding(0, 3, 0, 3),
		NWidgetFunction(MakeZxcvbKeys), SetPadding(0, 3, 0, 3),
		NWidgetFunction(MakeSpacebarKeys), SetPadding(0, 3, 0, 3),
	EndContainer(),
};

static const WindowDesc _osk_desc(
	WDP_CENTER, WDP_CENTER, 256, 140, 256, 140,
	WC_OSK, WC_NONE,
	WDF_STD_TOOLTIPS | WDF_STD_BTN | WDF_DEF_WIDGET | WDF_UNCLICK_BUTTONS,
	_osk_widgets, _nested_osk_widgets, lengthof(_nested_osk_widgets)
);

/**
 * Retrieve keyboard layout from language string or (if set) config file.
 * Also check for invalid characters.
 */
void GetKeyboardLayout()
{
	char keyboard[2][OSK_KEYBOARD_ENTRIES * 4 + 1];
	char errormark[2][OSK_KEYBOARD_ENTRIES + 1]; // used for marking invalid chars
	bool has_error = false; // true when an invalid char is detected

	if (StrEmpty(_keyboard_opt[0])) {
		GetString(keyboard[0], STR_OSK_KEYBOARD_LAYOUT, lastof(keyboard[0]));
	} else {
		strecpy(keyboard[0], _keyboard_opt[0], lastof(keyboard[0]));
	}

	if (StrEmpty(_keyboard_opt[1])) {
		GetString(keyboard[1], STR_OSK_KEYBOARD_LAYOUT_CAPS, lastof(keyboard[1]));
	} else {
		strecpy(keyboard[1], _keyboard_opt[1], lastof(keyboard[1]));
	}

	for (uint j = 0; j < 2; j++) {
		const char *kbd = keyboard[j];
		bool ended = false;
		for (uint i = 0; i < OSK_KEYBOARD_ENTRIES; i++) {
			_keyboard[j][i] = Utf8Consume(&kbd);

			/* Be lenient when the last characters are missing (is quite normal) */
			if (_keyboard[j][i] == '\0' || ended) {
				ended = true;
				_keyboard[j][i] = ' ';
				continue;
			}

			if (IsPrintable(_keyboard[j][i])) {
				errormark[j][i] = ' ';
			} else {
				has_error = true;
				errormark[j][i] = '^';
				_keyboard[j][i] = ' ';
			}
		}
	}

	if (has_error) {
		ShowInfoF("The keyboard layout you selected contains invalid chars. Please check those chars marked with ^.");
		ShowInfoF("Normal keyboard:  %s", keyboard[0]);
		ShowInfoF("                  %s", errormark[0]);
		ShowInfoF("Caps Lock:        %s", keyboard[1]);
		ShowInfoF("                  %s", errormark[1]);
	}
}

/**
 * Show the on-screen keyboard (osk) associated with a given textbox
 * @param parent pointer to the Window where this keyboard originated from
 * @param q      querystr_d pointer to the query string of the parent, which is
 *               shared for both windows
 * @param button widget number of parent's textbox
 * @param cancel widget number of parent's cancel button (0 if cancel events
 *               should not be passed)
 * @param ok     widget number of parent's ok button  (0 if ok events should not
 *               be passed)
 */
void ShowOnScreenKeyboard(QueryStringBaseWindow *parent, int button, int cancel, int ok)
{
	DeleteWindowById(WC_OSK, 0);

	GetKeyboardLayout();
	new OskWindow(&_osk_desc, parent, button, cancel, ok);
}
