MS native code and GTK

GTK (www.gtk.org) is an excellent free, open-source GUI toolkit. With Tor Lillqvist's win32 port, it provides a fine cross-platform solution. I regularly write GTK-based code under Linux, and as well as compiling it for that platform I am able to cross-compile it for win32 (see my cross-gtk page).

While you can get perfectly acceptable results using essentially the same source code for the Linux/unix and win32 versions of your program, it's possible to tweak the win32 version a little so that it conforms better to what Windows users expect, by using the win32 API directly for some functions (bracketed off by #ifdef). A couple of examples of this are shown below:

  1. Using "native" Microsoft file selection dialogs in place of gtkfilesel.
  2. Using the default windows font for menus and so on.

MS native file selection dialogs

There follows a snippet of code showing how one can set up a file selection function with a common prototype, implemented in two versions, one for X11 and one for win32. Some of the material is specific to the program of mine from which the code is extracted, but it should give you some idea of how to proceed. For further info, see the MS documentation for the win32 API. For instance, a google search on GetOpenFileName will quickly take you to the appropriate page on msdn.microsoft.com. 

/*
 *  Copyright (c) by Allin Cottrell
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

/* fileselect.c for gretl -- use the gtkextra file selector under X11,
   the native MS file selector under MS Windows */

#include "gretl.h"

extern void errbox (const char *msg); /* gretl function */

/* ........................................................... */

#ifdef G_OS_WIN32  /* native MS */

#include 

struct win32_filtermap {
    int action;
    char *filter;
};

static char *get_filters (int action)
{
    int i;
    char *filter;
    static struct win32_filtermap map[] = {
	{SAVE_DATA, "gretl data files (*.dat)\0*.dat\0all files\0*\0"},
	{SAVE_GZDATA, "compressed data files (*.gz)\0*.gz\0all files\0*\0"},
	{SAVE_BIN1, "gretl data files (*.dat)\0*.dat\0all files\0*\0"},
	{SAVE_BIN2, "gretl data files (*.dat)\0*.dat\0all files\0*\0"},
	{SAVE_CMDS, "gretl command files (*.inp)\0*.inp\0all files\0*\0"},
	{SAVE_SCRIPT, "gretl script files (*.inp)\0*.inp\0all files\0*\0"},
	{SAVE_CONSOLE, "gretl command files (*.inp)\0*.inp\0all files\0*\0"},
	{SAVE_MODEL, "text files (*.txt)\0*.txt\0all files\0*\0"},
	{SAVE_SESSION, "session files (*.gretl)\0*.gretl\0all files\0*\0"},
	{SAVE_LAST_GRAPH, "all files\0*\0"},
	{SAVE_GP_CMDS, "gnuplot files (*.gp)\0*.gp\0all files\0*\0"},
	{EXPORT_CSV, "CSV files (*.csv)\0*.csv\0all files\0*\0"},
	{EXPORT_R, "GNU R files (*.R)\0*.R\0all files\0*\0"},
	{EXPORT_R_ALT, "GNU R files (*.R)\0*.R\0all files\0*\0"},
	{EXPORT_OCTAVE, "GNU Octave files (*.m)\0*.m\0all files\0*\0"},
	{SAVE_OUTPUT, "text files (*.txt)\0*.txt\0all files\0*\0"},
	{SAVE_TEX_TAB, "TeX files (*.tex)\0*.tex\0all files\0*\0"},
	{SAVE_TEX_EQ, "TeX files (*.tex)\0*.tex\0all files\0*\0"},
	{OPEN_DATA, "gretl data files (*.dat)\0*.dat*\0all files\0*\0"},
	{OPEN_SCRIPT, "gretl script files (*.inp)\0*.inp\0all files\0*\0"},
	{OPEN_SESSION, "session files (*.gretl)\0*.gretl\0all files\0*\0"},
	{OPEN_CSV,  "CSV files (*.csv)\0*.csv\0all files\0*\0"},
	{OPEN_BOX, "BOX data files (*.box)\0*.box\0all files\0*\0"}};

    for (i=0; i< sizeof map/sizeof *map; i++) {
	if (action == map[i].action) {
	    filter = map[i].filter;
	    break;
	}
    }
    return filter;
}

/* ........................................................... */

void file_selector (char *msg, char *startdir, int action, gpointer data) 
{
    OPENFILENAME of;
    int retval;
    char fname[MAXLEN];

    fname[0] = '\0';

    /* initialize file dialog info struct */
    memset(&of, 0, sizeof of);
#ifdef OPENFILENAME_SIZE_VERSION_400
    of.lStructSize = OPENFILENAME_SIZE_VERSION_400;
#else
    of.lStructSize = sizeof of;
#endif
    of.hwndOwner = NULL;
    of.lpstrFilter = get_filters(action);
    of.lpstrCustomFilter = NULL;
    of.nFilterIndex = 1;
    of.lpstrFile = fname;
    of.nMaxFile = sizeof fname;
    of.lpstrFileTitle = NULL;
    of.lpstrInitialDir = startdir;
    of.lpstrTitle = msg;
    of.lpstrDefExt = NULL;
    of.Flags = OFN_HIDEREADONLY;

    if (action < END_OPEN)
	retval = GetOpenFileName(&of);
    else  /* a file save action */
	retval = GetSaveFileName(&of);

    if (!retval) {
	if (CommDlgExtendedError())
	    errbox("File dialog box error");
	return;
    }

    /* you now have the selected filename in "fname" and can
       do whatever is appropriate in response */

}

#else /* X11, not win32: use gtkextra */

struct extmap {
    int action;
    char *ext;
};

static char *get_filters (int action)
{
    int i;
    char *s = "*";
    static struct extmap map[] = {
	{SAVE_DATA, "*.dat"},
	{SAVE_GZDATA, "*.gz"},
	{SAVE_BIN1, "*.dat"},
	{SAVE_BIN2, "*.dat"},
	{SAVE_CMDS, "*.inp"},
	{SAVE_SCRIPT, "*.inp"},
	{SAVE_CONSOLE, "*.inp"},
	{SAVE_MODEL, "*.txt"},
	{SAVE_SESSION, "*.gretl"},
	{SAVE_GP_CMDS, "*.gp"},
	{EXPORT_CSV, "*.csv"},
	{EXPORT_R, "*.R"},
	{EXPORT_R_ALT, "*.R"},
	{EXPORT_OCTAVE, "*.m"},
	{SAVE_OUTPUT, "*.txt"},
	{SAVE_TEX_TAB, "*.tex"},
	{SAVE_TEX_EQ, "*.tex"},
	{OPEN_DATA, "*.dat*"},
	{OPEN_SCRIPT, "*.inp"},
	{OPEN_SESSION, "*.gretl"},
	{OPEN_CSV,  "*.csv"},
	{OPEN_BOX, "*.box"}};

    for (i=0; i < sizeof map / sizeof *map; i++) {
	if (action == map[i].action) {
	    s = map[i].ext;
	    break;
	}
    }
    return s;
}

/* ........................................................... */

static void filesel_callback (GtkWidget *w, gpointer data) 
{
    GtkIconFileSel *fs = GTK_ICON_FILESEL(data);
    gint action = GPOINTER_TO_INT(gtk_object_get_data
				  (GTK_OBJECT(data), "action"));
    char fname[MAXLEN];
    char *test, *path;

    test = gtk_entry_get_text(GTK_ENTRY(fs->file_entry));
    if (test == NULL || *test == '\0') 
	return;    
    path = gtk_file_list_get_path(GTK_FILE_LIST(fs->file_list));
    sprintf(fname, "%s%s", path, test);

    /* do something appropriate with the filename ... */

    gtk_widget_destroy(GTK_WIDGET(fs));
}

/* ........................................................... */

void file_selector (char *msg, char *startdir, int action, gpointer data) 
{
    GtkWidget *filesel;

    filesel = gtk_icon_file_selection_new(msg);
    if (strstr(startdir, "/."))
	gtk_icon_file_selection_show_hidden(GTK_ICON_FILESEL(filesel), TRUE);

    gtk_object_set_data(GTK_OBJECT(filesel), "action", GINT_TO_POINTER(action));

    gtk_icon_file_selection_set_filter(GTK_ICON_FILESEL(filesel), 
				       get_filters(action));
    gtk_signal_connect(GTK_OBJECT(GTK_ICON_FILESEL(filesel)->ok_button),
		       "clicked", 
		       (GtkSignalFunc) filesel_callback, filesel);

    gtk_icon_file_selection_open_dir(GTK_ICON_FILESEL(filesel), startdir);
    gtk_signal_connect_object(GTK_OBJECT(GTK_ICON_FILESEL
					 (filesel)->cancel_button),
			      "clicked", (GtkSignalFunc) gtk_widget_destroy,
			      GTK_OBJECT (filesel));
    gtk_widget_show(filesel);
}

#endif /* end of non-win32 stuff */

MS default font

The following code snippet shows how to grab the default Windows font and use it as the default font in your GTK program. The first version is for GTK 1.2; a version for GTK 2.0 follows.


#ifdef G_OS_WIN32
gchar *default_windows_menu_fontspec (void)
{
    gchar *fontspec = NULL;
    NONCLIENTMETRICS ncm;

    memset(&ncm, 0, sizeof ncm);
    ncm.cbSize = sizeof ncm;

    if (SystemParametersInfo(SPI_GETNONCLIENTMETRICS, ncm.cbSize, &ncm, 0)) {
	HDC screen = GetDC(0);
	double y_scale = 72.0 / GetDeviceCaps(screen, LOGPIXELSY);
	int pixel_size = (int) (ncm.lfMenuFont.lfHeight * y_scale);

	/* you may need to experiment with the size field */

	if (pixel_size < 0) pixel_size = -pixel_size;
	fontspec = g_strdup_printf("-*-%s-*-*-*-*-%i-*-*-*-p-*-iso8859-1",
				   ncm.lfMenuFont.lfFaceName,
				   pixel_size);
	
	ReleaseDC(0, screen);
    }

    return fontspec;
}
#endif

static GtkWidget *make_main_window (void) 
{
    GtkWidget *mwin;
#ifdef G_OS_WIN32
    gchar *winfont;
#endif

    mwin = gtk_window_new(GTK_WINDOW_TOPLEVEL);

#ifdef G_OS_WIN32
    winfont = default_windows_menu_fontspec();
    if (winfont != NULL) {
	GtkStyle *style = gtk_widget_get_style(mwin);

        style->font = gdk_font_load(winfont);
	if (style->font) {
	    gtk_widget_set_style(mwin, style);
	}
	g_free(winfont);
    }
#endif

    /* continue building main window ... */

}

End of GTK 1.2 version, now for GTK 2.0. (Ulf Lamping tells me this requires gtk 2.2.0 or higher to work properly.)


#ifdef G_OS_WIN32
static char appfontname[128] = "tahoma 8"; /* fallback value */
#else
static char appfontname[128] = "Sans 10";
#endif

void set_app_font (const char *fontname)
{
    GtkSettings *settings;

    if (fontname != NULL && *fontname == 0) return;

    settings = gtk_settings_get_default();

    if (fontname == NULL) {
	g_object_set(G_OBJECT(settings), "gtk-font-name", appfontname, NULL);
    } else {
	GtkWidget *w;
	PangoFontDescription *pfd;
	PangoContext *pc;
	PangoFont *pfont;

	w = gtk_label_new(NULL);
	pfd = pango_font_description_from_string(fontname);
	pc = gtk_widget_get_pango_context(w);
	pfont = pango_context_load_font(pc, pfd);

	if (pfont != NULL) {
	    strcpy(appfontname, fontname);
	    g_object_set(G_OBJECT(settings), "gtk-font-name", appfontname, NULL);
	}

	gtk_widget_destroy(w);
	pango_font_description_free(pfd);
    }
}

#ifdef G_OS_WIN32

char *default_windows_menu_fontspec (void)
{
    gchar *fontspec = NULL;
    NONCLIENTMETRICS ncm;

    memset(&ncm, 0, sizeof ncm);
    ncm.cbSize = sizeof ncm;

    if (SystemParametersInfo(SPI_GETNONCLIENTMETRICS, ncm.cbSize, &ncm, 0)) {
	HDC screen = GetDC(0);
	double y_scale = 72.0 / GetDeviceCaps(screen, LOGPIXELSY);
	int point_size = (int) (ncm.lfMenuFont.lfHeight * y_scale);

	if (point_size < 0) point_size = -point_size;
	fontspec = g_strdup_printf("%s %d", ncm.lfMenuFont.lfFaceName,
				   point_size);
	ReleaseDC(0, screen);
    }

    return fontspec;
}

static void try_to_get_windows_font (void)
{
    gchar *fontspec = default_windows_menu_fontspec();

    if (fontspec != NULL) {
	int match = 0;
	PangoFontDescription *pfd;
	PangoFont *pfont;
	PangoContext *pc;
	GtkWidget *w;

	pfd = pango_font_description_from_string(fontspec);

	w = gtk_label_new(NULL);
	pc = gtk_widget_get_pango_context(w);
	pfont = pango_context_load_font(pc, pfd);
	match = (pfont != NULL);

	pango_font_description_free(pfd);
	g_object_unref(G_OBJECT(pc));
	gtk_widget_destroy(w);

	if (match) set_app_font(fontspec);
	g_free(fontspec);
    }
}

#endif /* G_OS_WIN32 */

Allin Cottrell, Wake Forest University
cottrell@wfu.edu
Last updated: January, 2004