vgabios: Simplify scroll logic

Introduce a new function vgafb_scroll() to scroll a window on the
screen and update vgabios.c to use only that function for scrolling.
This makes the low-level vgafb_move_chars() and vgafb_clear_chars()
local to vgafb.c, and it simplifies the callers.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 14 insertions, 43 deletions

diff --git a/vgasrc/vgabios.c b/vgasrc/vgabios.c
index cfb6ba25..2c8cc79d 100644
--- a/vgasrc/vgabios.c
+++ b/vgasrc/vgabios.c
@@ -198,15 +198,10 @@ write_teletype(struct cursorpos *pcp, struct carattr ca)
     if (pcp->y > nbrows) {
         pcp->y--;
 
-        struct cursorpos dest = {0, 0, pcp->page};
-        struct cursorpos src = {0, 1, pcp->page};
-        struct cursorpos size = {GET_BDA(video_cols), nbrows};
-        vgafb_move_chars(dest, src, size);
-
-        struct cursorpos clr = {0, nbrows, pcp->page};
+        struct cursorpos win = {0, 0, pcp->page};
+        struct cursorpos winsize = {GET_BDA(video_cols), nbrows+1};
         struct carattr attr = {' ', 0, 0};
-        struct cursorpos clrsize = {GET_BDA(video_cols), 1};
-        vgafb_clear_chars(clr, attr, clrsize);
+        vgafb_scroll(win, winsize, 1, attr);
     }
 }
 
@@ -400,6 +395,7 @@ handle_1005(struct bregs *regs)
 static void
 verify_scroll(struct bregs *regs, int dir)
 {
+    // Verify parameters
     u8 ulx = regs->cl, uly = regs->ch, lrx = regs->dl, lry = regs->dh;
     u16 nbrows = GET_BDA(video_rows) + 1;
     if (lry >= nbrows)
@@ -410,41 +406,16 @@ verify_scroll(struct bregs *regs, int dir)
     int wincols = lrx - ulx + 1, winrows = lry - uly + 1;
     if (wincols <= 0 || winrows <= 0)
         return;
-
-    u8 page = GET_BDA(video_page);
-    int clearlines = regs->al, movelines = winrows - clearlines;
-    if (!clearlines || movelines <= 0) {
-        // Clear whole area.
-        struct cursorpos clr = {ulx, uly, page};
-        struct carattr attr = {' ', regs->bh, 1};
-        struct cursorpos clrsize = {wincols, winrows};
-        vgafb_clear_chars(clr, attr, clrsize);
-        return;
-    }
-
-    if (dir > 0) {
-        // Normal scroll
-        struct cursorpos dest = {ulx, uly, page};
-        struct cursorpos src = {ulx, uly + clearlines, page};
-        struct cursorpos size = {wincols, movelines};
-        vgafb_move_chars(dest, src, size);
-
-        struct cursorpos clr = {ulx, uly + movelines, page};
-        struct carattr attr = {' ', regs->bh, 1};
-        struct cursorpos clrsize = {wincols, clearlines};
-        vgafb_clear_chars(clr, attr, clrsize);
-    } else {
-        // Scroll down
-        struct cursorpos dest = {ulx, uly + clearlines, page};
-        struct cursorpos src = {ulx, uly, page};
-        struct cursorpos size = {wincols, movelines};
-        vgafb_move_chars(dest, src, size);
-
-        struct cursorpos clr = {ulx, uly, page};
-        struct carattr attr = {' ', regs->bh, 1};
-        struct cursorpos clrsize = {wincols, clearlines};
-        vgafb_clear_chars(clr, attr, clrsize);
-    }
+    int lines = regs->al;
+    if (lines >= winrows)
+        lines = 0;
+    lines *= dir;
+
+    // Scroll (or clear) window
+    struct cursorpos win = {ulx, uly, GET_BDA(video_page)};
+    struct cursorpos winsize = {wincols, winrows};
+    struct carattr attr = {' ', regs->bh, 1};
+    vgafb_scroll(win, winsize, lines, attr);
 }
 
 static void