> diff --git a/src/fileio_func.h b/src/fileio_func.h
> --- a/src/fileio_func.h
> +++ b/src/fileio_func.h
> @@ -14,6 +14,9 @@
>  
>  #include "fileio_type.h"
>  
> +/* Forward declaration. */
> +struct TarFileListEntry;
> +
>  void FioSeekTo(size_t pos, int mode);
>  void FioSeekToFile(uint8 slot, size_t pos);
>  size_t FioGetPos();
> @@ -23,6 +26,7 @@
>  uint32 FioReadDword();
>  void FioCloseAll();
>  void FioOpenFile(int slot, const char *filename, Subdirectory subdir);
> +FILE *FioFOpenFileTar(TarFileListEntry *entry, size_t *filesize);
>  void FioReadBlock(void *ptr, size_t size);
>  void FioSkipBytes(int n);
>  
> diff --git a/src/lang/english.txt b/src/lang/english.txt
> --- a/src/lang/english.txt
> +++ b/src/lang/english.txt
> @@ -2401,6 +2401,7 @@
>  STR_NEWGRF_SETTINGS_MOVEDOWN                                    :{BLACK}Move Down
>  STR_NEWGRF_SETTINGS_MOVEDOWN_TOOLTIP                            :{BLACK}Move the selected NewGRF file down the list
>  STR_NEWGRF_SETTINGS_FILE_TOOLTIP                                :{BLACK}A list of the NewGRF files that are installed. Click a file to change its parameters
> +STR_NEWGRF_SETTINGS_VIEW_README                                 :{BLACK}View Readme
>  
>  STR_NEWGRF_SETTINGS_SET_PARAMETERS                              :{BLACK}Set parameters
>  STR_NEWGRF_SETTINGS_TOGGLE_PALETTE                              :{BLACK}Toggle palette
> @@ -2434,6 +2435,9 @@
>  STR_NEWGRF_PARAMETERS_SETTING                                   :{STRING1}: {ORANGE}{STRING1}
>  STR_NEWGRF_PARAMETERS_NUM_PARAM                                 :{LTBLUE}Number of parameters: {ORANGE}{NUM}
>  
> +# NewGRF readme window
> +STR_NEWGRF_README_CAPTION                                       :{WHITE}View NewGRF Readme
> +
>  # NewGRF inspect window
>  STR_NEWGRF_INSPECT_CAPTION                                      :{WHITE}Inspect - {STRING5}
>  STR_NEWGRF_INSPECT_PARENT_BUTTON                                :{BLACK}Parent
> diff --git a/src/newgrf_config.cpp b/src/newgrf_config.cpp
> --- a/src/newgrf_config.cpp
> +++ b/src/newgrf_config.cpp
> @@ -22,6 +22,7 @@
>  
>  #include "fileio_func.h"
>  #include "fios.h"
> +#include "tar_type.h"
>  
>  /** Create a new GRFTextWrapper. */
>  GRFTextWrapper::GRFTextWrapper() :
> @@ -831,3 +832,28 @@
>  {
>  	return (this->ident.grfid & 0x00FFFFFF) == OPENTTD_GRAPHICS_BASE_GRF_ID;
>  }
> +
> +/**
> + * Search a grf tar archive for an accompanying readme.txt file.
> + * @param cfg The GRFConfig to search.
### Parameter doesn't exist?
> + * @return The TarFileListEntry for the readme,  \c NULL otherwise.
> + * @note A GRF can only have a readme if it is inside a tar archive.
> + * @todo Add a newgrf config flag.
> + */
> +TarFileListEntry *GRFConfig::GetReadme() const
> +{
> +	if (this->filename == NULL) return NULL;
> +
> +	const char *slash = strrchr(this->filename, PATHSEPCHAR);
> +	if (slash == NULL) return NULL;
> +	int prefix_length = slash - this->filename + 1; // Including the path separator.
> +	if (prefix_length + 10 + 1 > MAX_PATH) return NULL; // "foo/" + "readme.txt" + '\0' must fit.
> +
> +	char readme_path[MAX_PATH];
> +	memcpy(readme_path, this->filename, prefix_length);
> +	strecpy(readme_path + prefix_length, "readme.txt", lastof(readme_path));
> +
> +	TarFileList::iterator tar_entry = _tar_filelist.find(readme_path);
> +	if (tar_entry == _tar_filelist.end()) return NULL;
> +	return &(*tar_entry).second;
> +}
> diff --git a/src/newgrf_config.h b/src/newgrf_config.h
> --- a/src/newgrf_config.h
> +++ b/src/newgrf_config.h
> @@ -18,6 +18,8 @@
>  #include "misc/countedptr.hpp"
>  #include "fileio_type.h"
>  
> +struct TarFileListEntry;
> +
>  /** GRF config bit flags */
>  enum GCF_Flags {
>  	GCF_SYSTEM,     ///< GRF file is an openttd-internal system grf
> @@ -168,6 +170,8 @@
>  
>  	bool IsOpenTTDBaseGRF() const;
>  
> +	TarFileListEntry *GetReadme() const;
> +
>  	const char *GetName() const;
>  	const char *GetDescription() const;
>  
> diff --git a/src/newgrf_gui.cpp b/src/newgrf_gui.cpp
> --- a/src/newgrf_gui.cpp
> +++ b/src/newgrf_gui.cpp
> @@ -25,6 +25,7 @@
>  #include "core/geometry_func.hpp"
>  #include "newgrf_text.h"
>  #include "fileio_func.h"
> +#include "tar_type.h"
>  
>  #include "table/strings.h"
>  #include "table/sprites.h"
> @@ -446,7 +447,7 @@
>  	EndContainer(),
>  };
>  
> -/* Window definition for the change grf parameters window */
> +/** Window definition for the change grf parameters window */
>  static const WindowDesc _newgrf_parameters_desc(
>  	WDP_CENTER, 500, 208,
>  	WC_GRF_PARAMETERS, WC_NONE,
> @@ -460,6 +461,181 @@
>  	new NewGRFParametersWindow(&_newgrf_parameters_desc, c);
>  }
>  
> +/** Widgets of the #NewGRFReadmeWindow. */
> +enum ShowNewGRFReadmeWidgets {
> +	GRW_WIDGET_BACKGROUND, ///< Panel to draw the readme on.
> +	GRW_WIDGET_VSCROLLBAR, ///< Vertical scrollbar to scroll through the readme up-and-down.
> +	GRW_WIDGET_HSCROLLBAR, ///< Horizontal scrollbar to scroll through the readme left-to-right.
> +};
> +
> +/** Window for displaying the readme of a NewGRF. */
> +struct NewGRFReadmeWindow : public Window {
> +	GRFConfig *grf_config;               ///< View the readme of this GRFConfig.
> +	int line_height;                     ///< Height of a line in the display widget.
> +	Scrollbar *vscroll;                  ///< Vertical scrollbar.
> +	Scrollbar *hscroll;                  ///< Horizontal scrollbar.
> +	char *text;                          ///< Lines of text from the NewGRF's readme.
> +	SmallVector<const char *, 64> lines; ///< #text, split into lines in a table with lines.
> +	uint max_length;                     ///< The longest line in the readme (in pixels).
> +
> +	static const int top_spacing    = WD_FRAMETEXT_TOP;    ///< Additional spacing at the top of the #GRW_WIDGET_BACKGROUND widget.
> +	static const int bottom_spacing = WD_FRAMETEXT_BOTTOM; ///< Additional spacing at the bottom of the #GRW_WIDGET_BACKGROUND widget.
> +
> +
### Extra newline
> +	NewGRFReadmeWindow(const WindowDesc *desc, GRFConfig *c) : Window(), grf_config(c)
> +	{
> +		this->CreateNestedTree(desc);
> +		this->vscroll = this->GetScrollbar(GRW_WIDGET_VSCROLLBAR);
> +		this->hscroll = this->GetScrollbar(GRW_WIDGET_HSCROLLBAR);
> +		this->FinishInitNested(desc);
> +
> +		this->LoadReadme();
> +	}
> +
> +	~NewGRFReadmeWindow()
> +	{
> +		free(this->text);
> +	}
> +
> +	virtual void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize)
> +	{
> +		switch (widget) {
> +			case GRW_WIDGET_BACKGROUND:
> +				this->line_height = FONT_HEIGHT_NORMAL + 2;
> +				resize->height = this->line_height;
> +
> +				size->height = 4 * resize->height + this->top_spacing + this->bottom_spacing; // At least 4 lines are visible.
> +				size->width = max(200u, size->width); // At least 200 pixels wide.
> +				break;
> +		}
> +	}
> +
> +	virtual void DrawWidget(const Rect &r, int widget) const
> +	{
> +		if (widget != GRW_WIDGET_BACKGROUND) return;
> +
> +		DrawPixelInfo new_dpi;
> +		if (!FillDrawPixelInfo(&new_dpi, r.left + 1 , r.top + 1, r.right - r.left - 1, r.bottom - r.top - 1)) return;
### Why the +1 for left/top, and -1 for width/height?
> +
> +		DrawPixelInfo *old_dpi = _cur_dpi;
> +		_cur_dpi = &new_dpi;
> +
> +		int left = r.left + WD_FRAMETEXT_LEFT - this->hscroll->GetPosition();
### The dimensions passed to DrawString are relative to the DrawPixelInfo you set in FillDrawPixelInfo above, so there's no need to add r in
> +		int right = left + this->max_length;
> +		int top = r.top + WD_TEXTPANEL_TOP - this->line_height;
### Same here, and no need for - this->line_height. Also, why not use this->top_spacing instead of WD_TEXTPANEL_TOP directly?
> +		for (uint i = 0; i < this->lines.Length(); i++) {
> +			if (i >= this->vscroll->GetCapacity()) break;
> +			DrawString(left, right, top, this->lines[i + this->vscroll->GetPosition()], TC_WHITE);
> +			top += this->line_height;
> +		}
### This logic is a bit confused, see below.
> +
> +		_cur_dpi = old_dpi;
> +	}
> +
### Try something like this instead:
###   		DrawPixelInfo new_dpi;
###   		if (!FillDrawPixelInfo(&new_dpi, r.left, r.top, r.right - r.left + 1, r.bottom - r.top + 1)) return;
###   
###   		DrawPixelInfo *old_dpi = _cur_dpi;
###   		_cur_dpi = &new_dpi;
###   
###   		int left = WD_FRAMETEXT_LEFT - this->hscroll->GetPosition();
###   		int right = left + this->max_length;
###   		int top = this->top_spacing;
###   		for (uint i = 0; i < this->vscroll->GetCapacity() && i + this->vscroll->GetPosition() < this->lines.Length(); i++) {
###   			DrawString(left, right, top + i * this->line_height, this->lines[i + this->vscroll->GetPosition()], TC_WHITE);
###   		}

> +	virtual void OnResize()
> +	{
> +		this->vscroll->SetCapacityFromWidget(this, GRW_WIDGET_BACKGROUND);
### You need to pass in the vertical padding, since the count is calculated using the this->line_height (resize->height), like this:
###   this->vscroll->SetCapacityFromWidget(this, GRW_WIDGET_BACKGROUND, this->top_spacing + this->bottom_spacing);
> +		this->hscroll->SetCapacityFromWidget(this, GRW_WIDGET_BACKGROUND);
> +	}
> +
> +private:
### Missing newline
> +	/**
> +	 * Load the NewGRF's readme text from file, and setup #lines, #max_length, and both scrollbars.
> +	 */
> +	void LoadReadme()
> +	{
> +		this->text = NULL;
> +
> +		/* Does GRF have readme? */
> +		TarFileListEntry *tar_entry = this->grf_config->GetReadme();
> +		if (tar_entry == NULL) return;
> +
> +		/* Get text from file */
> +		size_t filesize;
> +		FILE *handle = FioFOpenFileTar(tar_entry, &filesize);
> +		if (handle == NULL) return;
> +		this->text = MallocT<char>(filesize + 1);
> +		if (fread(this->text, 1, filesize, handle) != filesize) {
> +			free(this->text);
> +			this->text = NULL;
> +			return;
> +		}
> +		fclose(handle);
> +		this->text[filesize] = '\0';
> +
> +		this->text = TrimWhitespace(this->text);
### This can adjust the value of this->text, so it cannot be passed to free() in the destructor anymore
### Also, why do this at all? The spaces in the first line with printable text might be used for indentation, like those in the following lines.
### All lines should be whitespace-trimmed, or none of them IMO.
### A better idea would be to just remove blank lines from the start/end of this->lines, which can be done after the next section
> +
> +		/* The first line is, of course, the beginning of the text. */
> +		this->lines.Clear();
> +		*this->lines.Append() = this->text;
> +
> +		/* Strip unprintable characters. */
> +		char *q = this->text;
> +		bool append_next = false;
> + 		for (char *p = this->text; *p != '\0'; p++) {
### There is a space before the tabs here
> +			if (append_next) {
> +				*this->lines.Append() = q;
> +				append_next = false;
> +			}
> +			if (*p == '\t') *q = ' '; // Change to a space
### What about something like "foo<tab>bar"? Perhaps use *q++ = ' ' instead
> +			if ((!IsPrintable(*p) && *p != '\n') || *p == '\r') continue;
> +
> +			if (*p == '\n') {
> +				*p = '\0';
> +				/* We want to append the next character. */
> +				append_next = true;
> +			}
> +			*q = *p; // Copy the character
> +			q++;
> +		}
> +		*q = '\0';
### Why not just use str_validate and get UTF-8 + internal sprite glyphs for free?
### At the least, this should perhaps be extracted out to a standalone function
> +
> +		/* Initialize scrollbars */
> +		this->vscroll->SetCount(this->lines.Length());
> +
> +		this->max_length = 0;
> +		for (uint i = 0; i < this->lines.Length(); i++) {
> +			this->max_length = max(this->max_length, GetStringBoundingBox(this->lines[i]).width);
> +		}
> +		this->hscroll->SetCount(this->max_length + WD_FRAMETEXT_LEFT + WD_FRAMETEXT_RIGHT);
> +		this->hscroll->SetStepSize(10); // Speed up horizontal scrollbar
> +	}
> +};
> +
> +static const NWidgetPart _nested_newgrf_readme_widgets[] = {
> +	NWidget(NWID_HORIZONTAL),
> +		NWidget(WWT_CLOSEBOX, COLOUR_MAUVE),
> +		NWidget(WWT_CAPTION, COLOUR_MAUVE), SetDataTip(STR_NEWGRF_README_CAPTION, STR_TOOLTIP_WINDOW_TITLE_DRAG_THIS),
> +		NWidget(WWT_SHADEBOX, COLOUR_MAUVE),
> +		NWidget(WWT_STICKYBOX, COLOUR_MAUVE),
> +	EndContainer(),
> +	NWidget(NWID_HORIZONTAL),
> +		NWidget(WWT_PANEL, COLOUR_MAUVE, GRW_WIDGET_BACKGROUND), SetMinimalSize(200, 125), SetResize(1, 12), SetScrollbar(GRW_WIDGET_VSCROLLBAR),
> +		EndContainer(),
> +		NWidget(NWID_VERTICAL),
> +			NWidget(NWID_VSCROLLBAR, COLOUR_MAUVE, GRW_WIDGET_VSCROLLBAR),
> +		EndContainer(),
> +	EndContainer(),
> +	NWidget(NWID_HORIZONTAL),
> +		NWidget(NWID_HSCROLLBAR, COLOUR_MAUVE, GRW_WIDGET_HSCROLLBAR),
> +		NWidget(WWT_RESIZEBOX, COLOUR_MAUVE),
> +	EndContainer(),
> +};
> +
> +/** Window definition for the grf readme window */
> +static const WindowDesc _newgrf_readme_desc(
> +	WDP_CENTER, 630, 460,
> +	WC_NEWGRF_README, WC_NONE,
> +	WDF_UNCLICK_BUTTONS,
> +	_nested_newgrf_readme_widgets, lengthof(_nested_newgrf_readme_widgets)
> +);
> +
> +void ShowNewGRFReadmeWindow(GRFConfig *c)
> +{
> +	DeleteWindowByClass(WC_NEWGRF_README);
> +	new NewGRFReadmeWindow(&_newgrf_readme_desc, c);
> +}
> +
>  static GRFPresetList _grf_preset_list;
>  
>  class DropDownListPresetItem : public DropDownListItem {
> @@ -497,6 +673,7 @@
>  	SNGRFS_SCROLL2BAR,
>  	SNGRFS_NEWGRF_INFO_TITLE,
>  	SNGRFS_NEWGRF_INFO,
> +	SNGRFS_NEWGRF_README,
>  	SNGRFS_SET_PARAMETERS,
>  	SNGRFS_TOGGLE_PALETTE,
>  	SNGRFS_APPLY_CHANGES,
> @@ -575,6 +752,7 @@
>  	~NewGRFWindow()
>  	{
>  		DeleteWindowByClass(WC_GRF_PARAMETERS);
> +		DeleteWindowByClass(WC_NEWGRF_README);
>  
>  		if (this->editable && !this->execute) {
>  			CopyGRFConfigList(this->orig_list, this->actives, true);
> @@ -942,6 +1120,16 @@
>  				this->DeleteChildWindows(WC_QUERY_STRING); // Remove the parameter query window
>  				break;
>  
> +			case SNGRFS_NEWGRF_README: { // View GRF readme
> +				if (this->active_sel == NULL && this->avail_sel == NULL) break;
> +
> +				GRFConfig *c;
> +				if (this->active_sel) c = this->active_sel;
> +				else c = new GRFConfig(*this->avail_sel);
### ifs with else branches don't use the single-line format. (http://wiki.openttd.org/Coding_guidelines#Control_flow) Perhaps use the ternary operator instead?
### Also, who deletes the new'd GRFConfig?
> +				ShowNewGRFReadmeWindow(c);
> +				break;
> +			}
> +
>  			case SNGRFS_SET_PARAMETERS: { // Edit parameters
>  				if (this->active_sel == NULL || !this->editable || !this->show_params || this->active_sel->num_valid_params == 0) break;
>  
> @@ -995,7 +1183,8 @@
>  		this->avail_sel = NULL;
>  		this->avail_pos = -1;
>  		this->avails.ForceRebuild();
> -		this->DeleteChildWindows(WC_QUERY_STRING); // Remove the parameter query window
> +		this->DeleteChildWindows(WC_QUERY_STRING);  // Remove the parameter query window
> +		this->DeleteChildWindows(WC_NEWGRF_README); // Remove the view readme window
>  	}
>  
>  	virtual void OnDropdownSelect(int widget, int index)
> @@ -1100,6 +1289,10 @@
>  			SNGRFS_MOVE_DOWN,
>  			WIDGET_LIST_END
>  		);
> +
> +		const GRFConfig *c = (this->avail_sel == NULL) ? this->active_sel : this->avail_sel;
> +		this->SetWidgetDisabledState(SNGRFS_NEWGRF_README, c == NULL || c->GetReadme() == NULL);
> +
>  		this->SetWidgetDisabledState(SNGRFS_SET_PARAMETERS, !this->show_params || disable_all || this->active_sel->num_valid_params == 0);
>  		this->SetWidgetDisabledState(SNGRFS_TOGGLE_PALETTE, disable_all);
>  
> @@ -1584,6 +1777,8 @@
>  	NWidget(WWT_PANEL, COLOUR_MAUVE), SetPadding(0, 0, 2, 0),
>  		NWidget(WWT_EMPTY, COLOUR_MAUVE, SNGRFS_NEWGRF_INFO_TITLE), SetFill(1, 0), SetResize(1, 0),
>  		NWidget(WWT_EMPTY, COLOUR_MAUVE, SNGRFS_NEWGRF_INFO), SetFill(1, 1), SetResize(1, 1), SetMinimalSize(150, 100),
> +		NWidget(WWT_PUSHTXTBTN, COLOUR_YELLOW, SNGRFS_NEWGRF_README), SetFill(1, 0), SetResize(1, 0),
> +				SetDataTip(STR_NEWGRF_SETTINGS_VIEW_README, STR_NULL), SetPadding(2, 2, 2, 2),
>  	EndContainer(),
>  	NWidget(NWID_SELECTION, INVALID_COLOUR, SNGRFS_SHOW_APPLY),
>  		/* Right side, buttons. */
> diff --git a/src/string.cpp b/src/string.cpp
> --- a/src/string.cpp
> +++ b/src/string.cpp
> @@ -546,6 +546,31 @@
>  	return length;
>  }
>  
> +/**
> + * Trim leading and trailing whitespace from a char.
### From a string, not a char.
> + * @param str the char to trim.
### Likewise
> + * @return the trimmed char.
### Likewise
> + */
> +char *TrimWhitespace(char *str)
> +{
> +	char *end;
> +
> +	/* Trim leading space */
> +	while(IsWhitespace(*str)) str++;
> +
> +	/* All spaces? */
> +	if(*str == '\0') return str;
> +
> +	/* Trim trailing space */
> +	end = str + strlen(str) - 1;
> +	while(end > str && isspace(*end)) end--;
### Why use isspace here, and IsWhitespace above?
> +
> +	/* Write new null terminator */
> +	*(end+1) = '\0';
### Spacing: *(end + 1)
> +
> +	return str;
> +}
> +
>  #ifdef DEFINE_STRNDUP
>  #include "core/math_func.hpp"
>  char *strndup(const char *s, size_t len)
> diff --git a/src/string_func.h b/src/string_func.h
> --- a/src/string_func.h
> +++ b/src/string_func.h
> @@ -79,6 +79,7 @@
>  size_t Utf8Encode(char *buf, WChar c);
>  size_t Utf8TrimString(char *s, size_t maxlen);
>  
> +char *TrimWhitespace(char *str);
>  
>  static inline WChar Utf8Consume(const char **s)
>  {
> diff --git a/src/window_type.h b/src/window_type.h
> --- a/src/window_type.h
> +++ b/src/window_type.h
> @@ -111,6 +111,7 @@
>  	WC_INDUSTRY_CARGOES,
>  	WC_GRF_PARAMETERS,
>  	WC_BUILD_OBJECT,
> +	WC_NEWGRF_README,
>  
>  	WC_INVALID = 0xFFFF
>  };