From c459b19780549efa9a422a5a82a6f38caee75445 Mon Sep 17 00:00:00 2001
From: tomsmeding <tom.smeding@gmail.com>
Date: Sat, 14 Jan 2017 23:29:23 +0100
Subject: Add pagedown implementation

---
 buffer.cpp | 41 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 36 insertions(+), 5 deletions(-)

diff --git a/buffer.cpp b/buffer.cpp
index 182c285..b8e0d75 100644
--- a/buffer.cpp
+++ b/buffer.cpp
@@ -189,6 +189,42 @@ void Buffer::handleCommand(const Command &cmd){
 		} else {
 			cursor.x=screen[sp.y].cells[sp.x].linex;
 		}
+	} else if(cmd[0]=="move_pagedown"){
+		Screenpos sp=findCursorInScreen();
+		if(sp.x==-1||screen.size()==0){
+			bel();
+			return;
+		}
+		i64 lastLine=screen.back().line;
+		i64 lastX=screen.back().cells.size()==0 ? screen.back().fromx : screen.back().cells.back().linex+1;
+		i64 newTopLine,newTopPart;
+		if(lastX>=tb.lineLen(lastLine)){
+			if(lastLine==tb.numLines()-1){
+				cursor.line=lastLine;
+				cursor.x=lastX;
+				return;
+			}
+			newTopLine=lastLine+1;
+			newTopPart=0;
+		} else {
+			newTopLine=lastLine;
+			newTopPart=screen.back().part+1;
+		}
+		vector<ScreenLine> screenCopy=screen;
+		renewLayout(newTopLine,newTopPart,lastWidth,lastHeight);
+		if((i64)screen.size()<lastHeight){
+			i64 gap=lastHeight-screen.size();
+			screen.insert(screen.begin(),screenCopy.begin()+(screenCopy.size()-gap),screenCopy.end());
+			cursor.line=screen.back().line;
+			if(screen.back().cells.size()==0)cursor.x=screen.back().fromx;
+			else cursor.x=screen.back().cells.back().linex+1;
+		} else {
+			cursor.line=screen[sp.y].line;
+			if((i64)screen[sp.y].cells.size()<sp.x){
+				if(screen[sp.y].cells.size()==0)cursor.x=screen[sp.y].fromx;
+				else cursor.x=screen[sp.y].cells.back().linex+1;
+			}
+		}
 	} else if(cmd[0]=="cancel"){
 		bel(); //nothing to cancel, apparently
 	} else {
@@ -347,11 +383,6 @@ 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(){
-- 
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