Try to match a fallback font if needed

Fixes #276

Instead of rendering the entire filename at once, Xft will let us do it
character by character. This will allow sxiv to query fontconfig for
a font that can provide any missing codepoints, if needed.

A known issue of this patch is that the "..." dots rendering will not
work properly for very long multibyte filenames. That is because we
cannot easily predict the final width of the rendered filename before
drawing it. I couldn't figure out a clean way to deal with this, so I
ended up just truncating the offending filenames.

1 files changed, 41 insertions, 6 deletions

diff --git a/window.c b/window.c
index 71d439f..46c3c6d 100644
--- a/window.c
+++ b/window.c
@@ -360,9 +360,40 @@ void win_clear(win_t *win)
 	XFillRectangle(e->dpy, win->buf.pm, gc, 0, 0, win->buf.w, win->buf.h);
 }
 
+void win_draw_bar_text(win_t *win, XftDraw *d, XftColor *color, XftFont *font, int x, int y, char *text, int maxlen, int maximum_x)
+{
+	size_t len = 0;
+	int xshift = 0, newshift;
+	long codep;
+	char *p, *nextp;
+	FcCharSet* fccharset;
+	XftFont* fallback = NULL;
+
+	for (p = text; *p && (len < maxlen); p = nextp, len++) {
+		nextp = utf8codepoint(p, &codep);
+		if (!XftCharExists(win->env.dpy, font, codep)) {
+			fccharset = FcCharSetCreate();
+			FcCharSetAddChar(fccharset, codep);
+			fallback = XftFontOpen(win->env.dpy, win->env.scr,
+					FC_CHARSET, FcTypeCharSet, fccharset,
+					FC_SCALABLE, FcTypeBool, FcTrue,
+					NULL);
+			FcCharSetDestroy(fccharset);
+		}
+		newshift = win_textwidth(&win->env, p, (int) (nextp-p), false, (fallback ? fallback : font));
+		if (xshift + newshift <= maximum_x)
+			XftDrawStringUtf8(d, color, (fallback ? fallback : font), x + xshift, y, (XftChar8*)p, (int) (nextp-p));
+		xshift += newshift;
+		if (fallback) {
+			XftFontClose(win->env.dpy, fallback);
+			fallback = NULL;
+		}
+	}
+}
+
 void win_draw_bar(win_t *win)
 {
-	int len, olen, x, y, w, tw;
+	int len, olen, x, y, w, tw, maximum_x;
 	char rest[3];
 	const char *dots = "...";
 	win_env_t *e;
@@ -385,7 +416,7 @@ void win_draw_bar(win_t *win)
 	XSetBackground(e->dpy, gc, win->bar.bgcol.pixel);
 
 	if ((len = strlen(r->buf)) > 0) {
-		if ((tw = win_textwidth(e, r->buf, len, true)) > w)
+		if ((tw = win_textwidth(e, r->buf, len, true, font)) > w)
 			return;
 		x = win->w - tw + H_TEXT_PAD;
 		w -= tw;
@@ -393,9 +424,10 @@ void win_draw_bar(win_t *win)
 	}
 	if ((len = strlen(l->buf)) > 0) {
 		olen = len;
-		while (len > 0 && (tw = win_textwidth(e, l->buf, len, true)) > w)
+		while (len > 0 && (tw = win_textwidth(e, l->buf, len, true, font)) > w)
 			len--;
 		if (len > 0) {
+			maximum_x = w;
 			if (len != olen) {
 				w = strlen(dots);
 				if (len <= w)
@@ -404,7 +436,7 @@ void win_draw_bar(win_t *win)
 				memcpy(l->buf + len - w, dots, w);
 			}
 			x = H_TEXT_PAD;
-			XftDrawStringUtf8(d, &win->bar.fgcol, font, x, y, (XftChar8*)l->buf, len);
+			win_draw_bar_text(win, d, &win->bar.fgcol, font, x, y, l->buf, len, maximum_x);
 			if (len != olen)
 			  memcpy(l->buf + len - w, rest, w);
 		}
@@ -437,11 +469,14 @@ void win_draw_rect(win_t *win, int x, int y, int w, int h, bool fill, int lw,
 		XDrawRectangle(win->env.dpy, win->buf.pm, gc, x, y, w, h);
 }
 
-int win_textwidth(const win_env_t *e, const char *text, unsigned int len, bool with_padding)
+int win_textwidth(const win_env_t *e, const char *text, unsigned int len, bool with_padding, XftFont *fnt)
 {
 	XGlyphInfo ext;
 
-	XftTextExtentsUtf8(e->dpy, font, (XftChar8*)text, len, &ext);
+	if(!fnt)
+		fnt = font;
+
+	XftTextExtentsUtf8(e->dpy, fnt, (XftChar8*)text, len, &ext);
 	return ext.xOff + (with_padding ? 2 * H_TEXT_PAD : 0);
 }