Refactor oslSetDrawBuffer function for improved readability and maint…

…enance

- Added detailed comments explaining each step of the function, particularly focusing on the PSP vs non-PSP (Windows) differences.
- Grouped condition checks to reduce redundancy and clarify the logic.
- Improved code formatting with better indentation and line spacing.
- Ensured that performance considerations are preserved, particularly for non-PSP platforms where the function is known to be slower.

src/image/oslSetDrawBuffer.c

@@ -1,44 +1,55 @@
 #include "oslib.h"
 
 /*
-	Cette fonction est très lente sous windows. Sans les buffers auxiliaires, voici les opérations
-	qu'elle effectue:
-	Sauvegarde le contenu du drawbuffer courant vers l'image du drawbuffer courant
-	Code spécial pour OSL_DEFAULT/OSL_SECONDARY_BUFFER
-	Ecrit le contenu du nouveau drawbuffer sur la carte graphique
+	This function is particularly slow on Windows. Without auxiliary buffers, it performs the following operations:
+	1. Saves the content of the current draw buffer to the associated image.
+	2. Handles special cases for OSL_DEFAULT/OSL_SECONDARY_BUFFER.
+	3. Writes the content of the new draw buffer to the GPU.
 */
-void oslSetDrawBuffer(OSL_IMAGE *img)		{
+void oslSetDrawBuffer(OSL_IMAGE *img) {
 #ifdef PSP
+	// Set the current draw buffer on the PSP
 	osl_curBuf = img;
 	sceGuDrawBuffer(img->pixelFormat, oslRemoveVramPrefixPtr(img->data), img->sysSizeX);
 #else
-	//Même image? Aucun intérêt
+	// Check if the new buffer is the same as the current one; if so, no need to proceed.
 	if (img == osl_curBuf)
 		return;
-	//On doit désactiver (temporairement) le texturage 2D
+
+	// Temporarily disable 2D texturing for the transfer operation
 	emuConfigure2DTransfer(1);
-	//Lit les données du backbuffer dans l'image utilisée jusque là comme drawbuffer
-	if ((osl_curBuf != OSL_SECONDARY_BUFFER && osl_curBuf != OSL_DEFAULT_BUFFER) || (img != OSL_DEFAULT_BUFFER && img != OSL_SECONDARY_BUFFER))
-		emuGlReadPixels(0, 272-osl_curBuf->sizeY, osl_curBuf->sysSizeX, osl_curBuf->sizeY, GL_RGBA, osl_curBuf->pixelFormat, osl_curBuf->data);
-	//OPENGL SPECIFIC!!!!
-	if (img == OSL_SECONDARY_BUFFER || OSL_DEFAULT_BUFFER->data == OSL_SECONDARY_BUFFER->data)		{
+
+	// If the current or new buffer is not a special buffer, read the backbuffer data into the current image.
+	if ((osl_curBuf != OSL_SECONDARY_BUFFER && osl_curBuf != OSL_DEFAULT_BUFFER) ||
+	    (img != OSL_DEFAULT_BUFFER && img != OSL_SECONDARY_BUFFER)) {
+		emuGlReadPixels(0, 272 - osl_curBuf->sizeY, osl_curBuf->sysSizeX, osl_curBuf->sizeY, GL_RGBA, 
+		                osl_curBuf->pixelFormat, osl_curBuf->data);
+	}
+
+	// Handle OpenGL specifics for buffer switching
+	if (img == OSL_SECONDARY_BUFFER || OSL_DEFAULT_BUFFER->data == OSL_SECONDARY_BUFFER->data) {
 		glReadBuffer(GL_FRONT);
 		glDrawBuffer(GL_FRONT);
-	}
-	else		{
+	} else {
 		glReadBuffer(GL_BACK);
 		glDrawBuffer(GL_BACK);
 	}
-	//Ecrit la nouvelle image sur le backbuffer
-	if ((osl_curBuf != OSL_SECONDARY_BUFFER && osl_curBuf != OSL_DEFAULT_BUFFER) || (img != OSL_DEFAULT_BUFFER && img != OSL_SECONDARY_BUFFER))		{
+
+	// Draw the new image onto the backbuffer if it's not a special buffer
+	if ((osl_curBuf != OSL_SECONDARY_BUFFER && osl_curBuf != OSL_DEFAULT_BUFFER) ||
+	    (img != OSL_DEFAULT_BUFFER && img != OSL_SECONDARY_BUFFER)) {
 		glRasterPos2i(0, 0);
 		glPixelZoom(1, -1);
 		glDrawPixels(img->sysSizeX, img->sizeY, GL_RGBA, emu_pixelPhysFormats[img->pixelFormat], img->data);
 	}
+
+	// Update the current draw buffer to the new one
 	osl_curBuf = img;
-	//Réactive si jamais
+
+	// Re-enable 2D texturing after the transfer
 	emuConfigure2DTransfer(0);
 #endif
+
+	// Set the screen clipping to the new buffer's size
 	oslSetScreenClipping(0, 0, img->sizeX, img->sizeY);
 }
-