vt: selection: take screen contents from uniscr if available

This preserves whatever was written even if we can't currently display the
given glyph.  Mouse paste won't corrupt any character of wcwidth() == 1
anymore.

Note that for now uniscr doesn't get allocated until something reads
/dev/vcsuN for that console, making this code dormant for most users.

Signed-off-by: Adam Borowski <kilobyte@angband.pl>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/vt/selection.c

@@ -57,11 +57,13 @@ static inline void highlight_pointer(const int where)
 	complement_pos(sel_cons, where);
 }
 
-static u16
+static u32
 sel_pos(int n)
 {
+	if (use_unicode)
+		return screen_glyph_unicode(sel_cons, n / 2);
 	return inverse_translate(sel_cons, screen_glyph(sel_cons, n),
-				use_unicode);
+				0);
 }
 
 /**
@@ -90,7 +92,8 @@ static u32 inwordLut[]={
   0x07FFFFFE, /* lowercase         */
 };
 
-static inline int inword(const u16 c) {
+static inline int inword(const u32 c)
+{
 	return c > 0x7f || (( inwordLut[c>>5] >> (c & 0x1F) ) & 1);
 }
 
@@ -167,7 +170,7 @@ int set_selection(const struct tiocl_selection __user *sel, struct tty_struct *t
 	struct tiocl_selection v;
 	char *bp, *obp;
 	int i, ps, pe, multiplier;
-	u16 c;
+	u32 c;
 	int mode;
 
 	poke_blanked_console();

drivers/tty/vt/vt.c

@@ -4543,6 +4543,16 @@ u16 screen_glyph(struct vc_data *vc, int offset)
 }
 EXPORT_SYMBOL_GPL(screen_glyph);
 
+u32 screen_glyph_unicode(struct vc_data *vc, int n)
+{
+	struct uni_screen *uniscr = get_vc_uniscr(vc);
+
+	if (uniscr)
+		return uniscr->lines[n / vc->vc_cols][n % vc->vc_cols];
+	return inverse_translate(vc, screen_glyph(vc, n * 2), 1);
+}
+EXPORT_SYMBOL_GPL(screen_glyph_unicode);
+
 /* used by vcs - note the word offset */
 unsigned short *screen_pos(struct vc_data *vc, int w_offset, int viewed)
 {

include/linux/selection.h

@@ -32,6 +32,7 @@ extern unsigned char default_blu[];
 
 extern unsigned short *screen_pos(struct vc_data *vc, int w_offset, int viewed);
 extern u16 screen_glyph(struct vc_data *vc, int offset);
+extern u32 screen_glyph_unicode(struct vc_data *vc, int offset);
 extern void complement_pos(struct vc_data *vc, int offset);
 extern void invert_screen(struct vc_data *vc, int offset, int count, int shift);