Backscrolling and misc future bugfixes

2 files changed, 40 insertions, 6 deletions

diff --git a/buffer.cpp b/buffer.cpp
index 1ace091..61cb15b 100644
--- a/buffer.cpp
+++ b/buffer.cpp
@@ -28,16 +28,25 @@ void Buffer::handleCommand(const Command &cmd){
 			return;
 		}
 		tb.read(file);
+		cursor.line=0;
+		cursor.x=0;
+		screen.clear();
 	} else if(cmd[0]=="insert_char"){
 		char c=cmd[1][0];
 		assert(c!='\n');
 		tb.insert(cursor.line,cursor.x,cmd[1][0]);
 		cursor.x++;
+		if(findCursorInScreen().x==-1){
+			screen.erase(screen.begin());
+		}
 		relayoutScreen();
 	} else if(cmd[0]=="insert_newline"){
 		tb.insert(cursor.line,cursor.x,'\n');
 		cursor.x=0;
 		cursor.line++;
+		if(findCursorInScreen().x==-1){
+			screen.erase(screen.begin());
+		}
 		relayoutScreen();
 	} else if(cmd[0]=="delete_backward"){
 		if(cursor.x==0&&cursor.line==0){
@@ -52,7 +61,11 @@ void Buffer::handleCommand(const Command &cmd){
 			cursor.x=tb.lineLen(cursor.line);
 			tb.erase(cursor.line,cursor.x);
 		}
-		relayoutScreen();
+		if(findCursorInScreen().x==-1){
+			scrollUp();
+		} else {
+			relayoutScreen();
+		}
 	} else if(cmd[0]=="delete_forward"){
 		if(cursor.line==tb.numLines()-1&&cursor.x==tb.lineLen(cursor.line)){
 			bel();
@@ -86,6 +99,9 @@ void Buffer::handleCommand(const Command &cmd){
 		} else {
 			cursor.x--;
 		}
+		if(findCursorInScreen().x==-1){
+			scrollUp();
+		}
 	} else if(cmd[0]=="move_downward"){
 		Screenpos sp=findCursorInScreen();
 		if(sp.x==-1){
@@ -110,10 +126,6 @@ void Buffer::handleCommand(const Command &cmd){
 		} else {
 			sp.y++;
 		}
-		if(sp.y>=(i64)screen.size()){
-			bel();
-			return;
-		}
 		cursor.line=screen[sp.y].line;
 		if(sp.x>=(i64)screen[sp.y].cells.size()){
 			cursor.x=tb.lineLen(cursor.line);
@@ -275,12 +287,33 @@ void Buffer::renewLayout(i64 topLine,i64 topPart,i64 width,i64 height){
 	if((i64)screen.size()>height){
 		screen.resize(height);
 	}
+
+	if(findCursorInScreen().x==-1){ //We lost the cursor! Let's find it again
+		performInitialLayout(width,height);
+		cerr<<"Re-performing initial layout because cursor was lost in renewLayout"<<endl;
+	}
 }
 
 void Buffer::relayoutScreen(){
 	renewLayout(screen[0].line,screen[0].part,lastWidth,lastHeight);
 }
 
+void Buffer::scrollUp(){
+	assert(screen.size()!=0);
+	if(screen[0].part>0){
+		renewLayout(screen[0].line,screen[0].part-1,lastWidth,lastHeight);
+		return;
+	}
+	if(screen[0].line==0){
+		bel();
+		return;
+	}
+
+	i64 topLine=screen[0].line-1;
+	screen=layoutLine(tb.getLine(topLine),topLine,lastWidth);
+	renewLayout(screen.back().line,screen.back().part,lastWidth,lastHeight);
+}
+
 //Returns {-1,-1} if not found
 Buffer::Screenpos Buffer::findCursorInScreen() const {
 	if(screen.size()==0)return {-1,-1};
@@ -325,7 +358,7 @@ void Buffer::show(i64 atx,i64 aty,i64 width,i64 height){
 
 	i64 gutterWidth=numberWidth(tb.numLines())+2;
 	i64 newWidth=width-gutterWidth;
-	if(newWidth!=lastWidth||height!=lastHeight){
+	if(newWidth!=lastWidth||height!=lastHeight||screen.size()==0){
 		if(lastWidth==-1)performInitialLayout(newWidth,height);
 		else renewLayout(screen[0].line,screen[0].part,newWidth,height);
 		lastWidth=newWidth;
diff --git a/buffer.h b/buffer.h
index 4c15703..64d7aa4 100644
--- a/buffer.h
+++ b/buffer.h
@@ -42,6 +42,7 @@ class Buffer{
 	void performInitialLayout(i64 width,i64 height);
 	void renewLayout(i64 topLine,i64 topPart,i64 width,i64 height);
 	void relayoutScreen();
+	void scrollUp();
 
 	Screenpos findCursorInScreen() const;