Fix bad math in moving the cursor when the window size changes.

2 files changed, 14 insertions, 19 deletions

diff --git a/app/src/main/java/de/mud/terminal/VDUBuffer.java b/app/src/main/java/de/mud/terminal/VDUBuffer.java
index 93e3ccf..f1d97ea 100644
--- a/app/src/main/java/de/mud/terminal/VDUBuffer.java
+++ b/app/src/main/java/de/mud/terminal/VDUBuffer.java
@@ -731,6 +731,7 @@ public class VDUBuffer {
     char cbuf[][];
     int abuf[][];
     int maxSize = bufSize;
+    int oldAbsR = screenBase + getCursorRow();
 
     if (w < 1 || h < 1) return;
 
@@ -778,14 +779,18 @@ public class VDUBuffer {
     int C = getCursorColumn();
     if (C < 0)
       C = 0;
-    else if (C >= width)
-      C = width - 1;
+    else if (C >= w)
+      C = w - 1;
 
     int R = getCursorRow();
+    // If the screen size has grown and now there are more rows on the screen,
+    // slide the cursor down to the end of the text.
+    if (R + screenBase <= oldAbsR)
+      R = oldAbsR - screenBase;
     if (R < 0)
       R = 0;
-    else if (R >= height)
-      R = height - 1;
+    else if (R >= h)
+      R = h - 1;
 
     setCursorPosition(C, R);
 
diff --git a/app/src/main/java/de/mud/terminal/vt320.java b/app/src/main/java/de/mud/terminal/vt320.java
index ab4a90d..dc95bea 100644
--- a/app/src/main/java/de/mud/terminal/vt320.java
+++ b/app/src/main/java/de/mud/terminal/vt320.java
@@ -162,23 +162,13 @@ public void setScreenSize(int c, int r, boolean broadcast) {
 
     super.setScreenSize(c,r,false);
 
-    boolean cursorChanged = false;
-
-    // Don't let the cursor go off the screen.
-    if (C >= c) {
-      C = c - 1;
-      cursorChanged = true;
-    }
-
+    // Don't let the cursor go off the screen. Scroll down if needed.
     if (R >= r) {
-      R = r - 1;
-      cursorChanged = true;
-    }
-
-    if (cursorChanged) {
-      setCursorPosition(C, R);
-      redraw();
+      screenBase += R - (r - 1);
+      setWindowBase(screenBase);
     }
+    R = getCursorRow();
+    C = getCursorColumn();
 
     if (broadcast) {
       setWindowSize(c, r); /* broadcast up */