display: initialize the colors only when starting to draw the content

This avoids https://savannah.gnu.org/bugs/?49912 while at the same time
avoiding to draw the edit window twice in a row -- the first drawing
would use a wrong margin, which results in a visible and irritating
shift left or right of the content upon the second drawing.

This fixes https://savannah.gnu.org/bugs/?50877.

src/color.c

@@ -132,6 +132,8 @@ void color_init(void)
 	fprintf(stderr, "init_pair(): fg = %hd, bg = %hd\n", foreground, background);
 #endif
     }
+
+    have_palette = TRUE;
 }
 
 /* Try to match the given shibboleth string with one of the regexes in

src/files.c

@@ -589,8 +589,7 @@ void display_buffer(void)
 	titlebar(NULL);
 
 #ifndef DISABLE_COLOR
-    /* Make sure we're using the buffer's associated colors. */
-    color_init();
+    have_palette = FALSE;
 
     /* If there are multiline coloring regexes, and there is no
      * multiline cache data yet, precalculate it now. */
@@ -599,8 +598,7 @@ void display_buffer(void)
 	precalc_multicolorinfo();
 #endif
 
-    /* Update the content of the edit window straightaway. */
-    edit_refresh();
+    refresh_needed = TRUE;
 }
 
 #ifndef DISABLE_MULTIBUFFER

src/global.c

@@ -52,6 +52,11 @@ int margin = 0;
 int editwincols = -1;
 	/* The number of usable columns in the edit window: COLS - margin. */
 
+#ifndef DISABLE_COLOR
+bool have_palette = FALSE;
+	/* Whether the colors for the current syntax have been initialized. */
+#endif
+
 message_type lastmessage = HUSH;
 	/* Messages of type HUSH should not overwrite type MILD nor ALERT. */
 

src/proto.h

@@ -43,6 +43,10 @@ extern bool as_an_at;
 extern int margin;
 extern int editwincols;
 
+#ifndef DISABLE_COLOR
+extern bool have_palette;
+#endif
+
 extern message_type lastmessage;
 
 extern filestruct *pletion_line;

src/winio.c

@@ -3054,6 +3054,12 @@ void edit_refresh(void)
     filestruct *line;
     int row = 0;
 
+#ifndef DISABLE_COLOR
+    /* When needed, initialize the colors for the current syntax. */
+    if (!have_palette)
+	color_init();
+#endif
+
     /* If the current line is out of view, get it back on screen. */
     if (current_is_offscreen()) {
 #ifdef DEBUG