From 8531162bd9761ce49016b3738ddf394b28f8e462 Mon Sep 17 00:00:00 2001
From: Zack Middleton <zturtleman@gmail.com>
Date: Fri, 16 Oct 2015 19:18:38 -0500
Subject: [PATCH] Fix not swapping buffers because out of cmd buffer space

Reserve space for end of list and swap buffer commands. These are absolutely
required and cannot be dropped. Dropping swap buffer command causes screen
to not update and possible crash from drawsurf buffer overflow if not enough
cmd buffer space for many continous frames.
---
 code/renderergl1/tr_cmds.c | 19 +++++++++++++++----
 code/renderergl2/tr_cmds.c | 19 +++++++++++++++----
 2 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/code/renderergl1/tr_cmds.c b/code/renderergl1/tr_cmds.c
index 00b819ac..19094700 100644
--- a/code/renderergl1/tr_cmds.c
+++ b/code/renderergl1/tr_cmds.c
@@ -114,19 +114,19 @@ void R_IssuePendingRenderCommands( void ) {
 
 /*
 ============
-R_GetCommandBuffer
+R_GetCommandBufferReserved
 
 make sure there is enough command space
 ============
 */
-void *R_GetCommandBuffer( int bytes ) {
+void *R_GetCommandBufferReserved( int bytes, int reservedBytes ) {
 	renderCommandList_t	*cmdList;
 
 	cmdList = &backEndData->commands;
 	bytes = PAD(bytes, sizeof(void *));
 
 	// always leave room for the end of list command
-	if ( cmdList->used + bytes + 4 > MAX_RENDER_COMMANDS ) {
+	if ( cmdList->used + bytes + 4 + reservedBytes > MAX_RENDER_COMMANDS ) {
 		if ( bytes > MAX_RENDER_COMMANDS - 4 ) {
 			ri.Error( ERR_FATAL, "R_GetCommandBuffer: bad size %i", bytes );
 		}
@@ -139,6 +139,17 @@ void *R_GetCommandBuffer( int bytes ) {
 	return cmdList->cmds + cmdList->used - bytes;
 }
 
+/*
+=============
+R_GetCommandBuffer
+
+returns NULL if there is not enough space for important commands
+=============
+*/
+void *R_GetCommandBuffer( int bytes ) {
+	return R_GetCommandBufferReserved( bytes, sizeof ( swapBuffersCommand_t ) );
+}
+
 
 /*
 =============
@@ -454,7 +465,7 @@ void RE_EndFrame( int *frontEndMsec, int *backEndMsec ) {
 	if ( !tr.registered ) {
 		return;
 	}
-	cmd = R_GetCommandBuffer( sizeof( *cmd ) );
+	cmd = R_GetCommandBufferReserved( sizeof( *cmd ), 0 );
 	if ( !cmd ) {
 		return;
 	}
diff --git a/code/renderergl2/tr_cmds.c b/code/renderergl2/tr_cmds.c
index 18fd69c3..0f48727d 100644
--- a/code/renderergl2/tr_cmds.c
+++ b/code/renderergl2/tr_cmds.c
@@ -121,19 +121,19 @@ void R_IssuePendingRenderCommands( void ) {
 
 /*
 ============
-R_GetCommandBuffer
+R_GetCommandBufferReserved
 
 make sure there is enough command space
 ============
 */
-void *R_GetCommandBuffer( int bytes ) {
+void *R_GetCommandBufferReserved( int bytes, int reservedBytes ) {
 	renderCommandList_t	*cmdList;
 
 	cmdList = &backEndData->commands;
 	bytes = PAD(bytes, sizeof(void *));
 
 	// always leave room for the end of list command
-	if ( cmdList->used + bytes + 4 > MAX_RENDER_COMMANDS ) {
+	if ( cmdList->used + bytes + 4 + reservedBytes > MAX_RENDER_COMMANDS ) {
 		if ( bytes > MAX_RENDER_COMMANDS - 4 ) {
 			ri.Error( ERR_FATAL, "R_GetCommandBuffer: bad size %i", bytes );
 		}
@@ -146,6 +146,17 @@ void *R_GetCommandBuffer( int bytes ) {
 	return cmdList->cmds + cmdList->used - bytes;
 }
 
+/*
+=============
+R_GetCommandBuffer
+
+returns NULL if there is not enough space for important commands
+=============
+*/
+void *R_GetCommandBuffer( int bytes ) {
+	return R_GetCommandBufferReserved( bytes, sizeof ( swapBuffersCommand_t ) );
+}
+
 
 /*
 =============
@@ -525,7 +536,7 @@ void RE_EndFrame( int *frontEndMsec, int *backEndMsec ) {
 	if ( !tr.registered ) {
 		return;
 	}
-	cmd = R_GetCommandBuffer( sizeof( *cmd ) );
+	cmd = R_GetCommandBufferReserved( sizeof( *cmd ), 0 );
 	if ( !cmd ) {
 		return;
 	}