Scrolling up and scrolling down

src/text_editor/math.cpp

@@ -23,6 +23,18 @@ Vec2 GetSize(Rect2 r) {
     return result;
 }
 
+Vec2I GetSize(Rect2I r) {
+    Vec2I result = {(r.max.x - r.min.x), (r.max.y - r.min.y)};
+    return result;
+}
+
+Vec2 GetSizeF(Rect2I r) {
+    Vec2 result = {(float)(r.max.x - r.min.x), (float)(r.max.y - r.min.y)};
+    return result;
+}
+
+Vec2 ToVec2(Vec2I v) { return {(float)v.x, (float)v.y}; }
+
 // clang-format off
 Rect2 operator-(Rect2 r, Rect2 value) { return { r.min.x - value.min.x, r.min.y - value.min.y, r.max.x - value.max.x, r.max.y - value.max.y }; }
 Rect2 operator+(Rect2 r, Rect2 value) { return { r.min.x + value.min.x, r.min.y + value.min.y, r.max.x + value.max.x, r.max.y + value.max.y }; }

src/text_editor/view.cpp

@@ -123,8 +123,9 @@ Int MoveCursor(Buffer &buffer, Int pos, int direction, bool ctrl_pressed) {
 }
 
 void HandleKeybindings(View *_view) {
-    View   &view = *_view;
-    Buffer &buf  = *view.buffer;
+    View   &view                       = *_view;
+    Buffer &buf                        = *view.buffer;
+    Cursor  main_cursor_on_begin_frame = view.cursors[0];
 
     if (IsKeyDown(KEY_F1)) {
         view.scroll.x -= GetMouseWheelMove() * 48;
@@ -147,6 +148,33 @@ void HandleKeybindings(View *_view) {
         }
     }
 
+    // @todo: this should happen after we calculate rect for the view
+    // Usually in other text editors apart from view there is also a 'window'
+    // abstraction which is exactly the thing which shows the view, will need
+    // to think about this later
+    if (!AreEqual(main_cursor_on_begin_frame, view.cursors[0])) {
+
+        Cursor c     = view.cursors[0];
+        Int    front = GetFront(c);
+        Int    line  = PosToLine(buf, front);
+
+        Rect2I GetVisibleCells(const View &view);
+        Rect2I visible       = GetVisibleCells(view);
+        Vec2I  visible_cells = GetSize(visible);
+        Vec2   visible_size  = ToVec2(visible_cells) * Vec2{view.char_spacing, view.line_spacing};
+        Vec2   rect_size     = GetSize(view.rect);
+
+        if (line > visible.max.y - 3) {
+            Int   set_view_at_line = line - (visible_cells.y - 1);
+            float cut_off_y        = Max(0.f, visible_size.y - rect_size.y);
+            view.scroll.y          = ((float)set_view_at_line * view.line_spacing) + cut_off_y;
+        }
+
+        if (line < visible.min.y + 1) {
+            view.scroll.y = line * view.line_spacing;
+        }
+    }
+
     // Clip scroll
     {
         Int last_line = LastLine(view.buffer[0]);

src/text_editor/view_draw.cpp

@@ -1,4 +1,3 @@
-
 Rect2I GetVisibleCells(const View &view) {
     Vec2  size = GetSize(view.rect);
     float _cx  = size.x / view.char_spacing;