Rewrote the manual paging code

Nebuleon spotted a bug in TextManualDialog where the unsigned value
'pages[page].text.size() - rowsPerPage' could wrap around at 0 for
short chapters. I decided to change a bit more than just fixing the
bug though.

src/textdialog.cpp

@@ -23,6 +23,8 @@
 #include "gmenu2x.h"
 #include "utilities.h"
 
+#include <algorithm>
+
 using namespace std;
 
 TextDialog::TextDialog(GMenu2X *gmenu2x, const string &title, const string &description, const string &icon, const string &text)
@@ -79,6 +81,8 @@ void TextDialog::exec() {
 	unsigned int contentY, contentHeight;
 	tie(contentY, contentHeight) = gmenu2x->getContentArea();
 	const unsigned rowsPerPage = contentHeight / fontHeight;
+	const unsigned maxFirstRow =
+			text.size() < rowsPerPage ? 0 : text.size() - rowsPerPage;
 	contentY += (contentHeight % fontHeight) / 2;
 
 	unsigned firstRow = 0;
@@ -94,19 +98,14 @@ void TextDialog::exec() {
 				if (firstRow > 0) firstRow--;
 				break;
 			case InputManager::DOWN:
-				if (firstRow + rowsPerPage < text.size()) firstRow++;
+				if (firstRow < maxFirstRow) firstRow++;
 				break;
 			case InputManager::ALTLEFT:
-				if (firstRow >= rowsPerPage-1) firstRow -= rowsPerPage-1;
+				if (firstRow >= rowsPerPage - 1) firstRow -= rowsPerPage - 1;
 				else firstRow = 0;
 				break;
 			case InputManager::ALTRIGHT:
-				if (firstRow + rowsPerPage*2 -1 < text.size()) {
+				firstRow = min(firstRow + rowsPerPage - 1, maxFirstRow);
-					firstRow += rowsPerPage-1;
-				} else {
-					firstRow = text.size() < rowsPerPage ?
-						0 : text.size() - rowsPerPage;
-				}
 				break;
 			case InputManager::SETTINGS:
 			case InputManager::CANCEL:

src/textmanualdialog.cpp

@@ -68,9 +68,6 @@ TextManualDialog::TextManualDialog(GMenu2X *gmenu2x, const string &title, const
 }
 
 void TextManualDialog::exec() {
-	bool close = false;
-	uint page=0;
-
 	Surface bg(gmenu2x->bg);
 
 	//link icon
@@ -89,13 +86,17 @@ void TextManualDialog::exec() {
 
 	bg.convertToDisplayFormat();
 
-	uint firstRow = 0, rowsPerPage = 180/gmenu2x->font->getLineSpacing();
 	stringstream ss;
 	ss << pages.size();
 	string spagecount;
 	ss >> spagecount;
 	string pageStatus;
 
+	const unsigned rowsPerPage = 180 / gmenu2x->font->getLineSpacing();
+
+	unsigned page = 0, firstRow = 0;
+	bool close = false;
+
 	while (!close) {
 		Surface& s = *gmenu2x->s;
 
@@ -111,12 +112,15 @@ void TextManualDialog::exec() {
 
 		s.flip();
 
+		const unsigned maxFirstRow = pages[page].text.size() < rowsPerPage
+				? 0 : pages[page].text.size() - rowsPerPage;
+
 		switch(gmenu2x->input.waitForPressedButton()) {
 			case InputManager::UP:
 				if (firstRow > 0) firstRow--;
 				break;
 			case InputManager::DOWN:
-				if (firstRow + rowsPerPage < pages[page].text.size()) firstRow++;
+				if (firstRow < maxFirstRow) firstRow++;
 				break;
 			case InputManager::LEFT:
 				if (page > 0) {
@@ -131,12 +135,11 @@ void TextManualDialog::exec() {
 				}
 				break;
 			case InputManager::ALTLEFT:
-				if (firstRow >= rowsPerPage-1) firstRow -= rowsPerPage-1;
+				if (firstRow >= rowsPerPage - 1) firstRow -= rowsPerPage - 1;
 				else firstRow = 0;
 				break;
 			case InputManager::ALTRIGHT:
-				if (firstRow + rowsPerPage*2 -1 < pages[page].text.size()) firstRow += rowsPerPage-1;
+				firstRow = min(firstRow + rowsPerPage - 1, maxFirstRow);
-				else firstRow = max(0ul, (unsigned long) (pages[page].text.size() - rowsPerPage));
 				break;
 			case InputManager::CANCEL:
 			case InputManager::SETTINGS: