From b860c82d879e184c82eec1fd1c263b2f06d0d3ab Mon Sep 17 00:00:00 2001
From: churl <tobi@urpost.de>
Date: Tue, 10 May 2022 00:20:25 +0200
Subject: [PATCH] fix bufferedcga bug where buffer was used before init

---
 c_os/devices/BufferedCGA.cc | 54 ++++++++++++++++++++++---------------
 c_os/devices/BufferedCGA.h  |  8 +++---
 2 files changed, 37 insertions(+), 25 deletions(-)

diff --git a/c_os/devices/BufferedCGA.cc b/c_os/devices/BufferedCGA.cc
index 86fdba0..a63b2fe 100755
--- a/c_os/devices/BufferedCGA.cc
+++ b/c_os/devices/BufferedCGA.cc
@@ -10,12 +10,16 @@ void BufferedCGA::init() {
 }
 
 void BufferedCGA::displaypage() {
-    if (this->current_page == 0) {
-        // Use pagebuffer
-        this->scrollback_buffer->copy_page_from_pagebuffer((cga_page_t*)CGA_START);
+    if (this->initialized) {
+        if (this->current_page == 0) {
+            // Use pagebuffer
+            this->scrollback_buffer->copy_page_from_pagebuffer((cga_page_t*)CGA_START);
+        } else {
+            // Use scrollback
+            this->scrollback_buffer->copy_page_from_buffer((cga_line_t*)CGA_START, this->current_page - 1);
+        }
     } else {
-        // Use scrollback
-        this->scrollback_buffer->copy_page_from_buffer((cga_line_t*)CGA_START, this->current_page - 1);
+        this->print("ScrollbackBuffer not initialized\n\n", 34);
     }
 }
 
@@ -51,25 +55,33 @@ void BufferedCGA::clear() {
     }
 }
 
-unsigned int BufferedCGA::scroll_page_backward() {
-    // If this is the first scrollback we have to save the current screen content
-    if (this->current_page == 0) {
-        this->scrollback_buffer->copy_page_to_pagebuffer((cga_page_t*)CGA_START);
-    }
+void BufferedCGA::scroll_page_backward() {
+    if (this->initialized) {
 
-    // current_page can be equal to scrollback_buffer->pages
-    // as we have a separate pagebuffer for the current screen content
-    if (this->current_page < this->scrollback_buffer->pages) {
-        this->current_page = this->current_page + 1;
+        // If this is the first scrollback we have to save the current screen content
+        if (this->current_page == 0) {
+            this->scrollback_buffer->copy_page_to_pagebuffer((cga_page_t*)CGA_START);
+        }
+
+        // current_page can be equal to scrollback_buffer->pages
+        // as we have a separate pagebuffer for the current screen content
+        if (this->current_page < this->scrollback_buffer->pages) {
+            this->current_page = this->current_page + 1;
+        }
+        this->displaypage();
+    } else {
+        this->print("ScrollbackBuffer not initialized\n\n", 34);
     }
-    this->displaypage();
-    return this->current_page;
 }
 
-unsigned int BufferedCGA::scroll_page_forward() {
-    if (this->current_page > 0) {
-        this->current_page = this->current_page - 1;
+void BufferedCGA::scroll_page_forward() {
+    if (this->initialized) {
+
+        if (this->current_page > 0) {
+            this->current_page = this->current_page - 1;
+        }
+        this->displaypage();
+    } else {
+        this->print("ScrollbackBuffer not initialized\n\n", 34);
     }
-    this->displaypage();
-    return this->current_page;
 }
diff --git a/c_os/devices/BufferedCGA.h b/c_os/devices/BufferedCGA.h
index 77024a4..c9550f8 100755
--- a/c_os/devices/BufferedCGA.h
+++ b/c_os/devices/BufferedCGA.h
@@ -19,10 +19,10 @@ private:
 public:
     BufferedCGA() : CGA(), initialized(false), current_page(0) {};
 
-    void init();                          // Scrollback needs to be initialized after memorymanagement
-    unsigned char current_page;           // The page that is displayed
-    unsigned int scroll_page_backward();  // Scroll up the page history
-    unsigned int scroll_page_forward();   // Scroll down the page history (to the current page)
+    void init();                  // Scrollback needs to be initialized after memorymanagement
+    unsigned char current_page;   // The page that is displayed
+    void scroll_page_backward();  // Scroll up the page history
+    void scroll_page_forward();   // Scroll down the page history (to the current page)
 
     void print(char* string, int n, unsigned char attrib = STD_ATTR) override;
     void scrollup() override;