GenerateThumbnailForURL.m

#include <CoreFoundation/CoreFoundation.h>
#include <CoreServices/CoreServices.h>
#include <QuickLook/QuickLook.h>
#import <Cocoa/Cocoa.h>
#import "CSVDocument.h"
#import "CSVRowObject.h"

#define THUMB_SIZE 512.0
#define ASPECT 0.8			// aspect ratio
#define NUM_ROWS 18
#define BADGE_CSV @"csv"
#define BADGE_TSV @"tab"

static CGContextRef createRGBABitmapContext(CGSize pixelSize);
//static CGContextRef createVectorContext(CGSize pixelSize)


/**
 *  Generate a thumbnail for file.
 *
 *  This function's job is to create thumbnail for designated file as fast as possible.
 */
OSStatus GenerateThumbnailForURL(void *thisInterface, QLThumbnailRequestRef thumbnail, CFURLRef url, CFStringRef contentTypeUTI, CFDictionaryRef options, CGSize maxSize)
{
	@autoreleasepool {
		NSURL *myURL = (__bridge NSURL *)url;
		NSError *theErr = nil;
		
		// Load document data using NSStrings house methods
		// For huge files, maybe guess file encoding using `file --brief --mime` and use NSFileHandle? Not for now...
		NSStringEncoding stringEncoding;
		NSString *fileString = [NSString stringWithContentsOfURL:myURL usedEncoding:&stringEncoding error:&theErr];
		
		// We could not open the file, probably unknown encoding; try ISO-8859-1
		if (!fileString) {
			stringEncoding = NSISOLatin1StringEncoding;
			fileString = [NSString stringWithContentsOfURL:myURL encoding:stringEncoding error:&theErr];
			
			// Still no success, give up
			if (!fileString) {
				if (nil != theErr) {
					NSLog(@"Error opening the file: %@", theErr);
				}
				
				return noErr;
			}
		}
		
		
		// Parse the data if still interested in the thumbnail
		if (false == QLThumbnailRequestIsCancelled(thumbnail)) {
			CSVDocument *csvDoc = [CSVDocument new];
			csvDoc.autoDetectSeparator = YES;
			NSUInteger gotRows = [csvDoc numRowsFromCSVString:fileString maxRows:NUM_ROWS error:NULL];
			
			CGFloat rowHeight = ceilf(THUMB_SIZE / MIN(MAX(4, gotRows), NUM_ROWS));
			CGFloat fontSize = roundf(0.666 * rowHeight);
			
			// Draw an icon if still interested in the thumbnail
			if ((gotRows > 0) && (false == QLThumbnailRequestIsCancelled(thumbnail))) {
				CGRect maxBounds = CGRectMake(0.f, 0.f, THUMB_SIZE, THUMB_SIZE);
				CGRect usedBounds = CGRectMake(0.f, 0.f, 0.f, 0.f);
				CGFloat badgeMaxSize = THUMB_SIZE;
				
				CGContextRef context = createRGBABitmapContext(maxBounds.size);
				//CGContextRef context = createVectorContext(maxBounds.size);
				if (context) {
					//CGPDFContextBeginPage(context, NULL);
					
					// Flip CoreGraphics coordinate system
					CGContextScaleCTM(context, 1.f, -1.f);
					CGContextTranslateCTM(context, 0, -maxBounds.size.height);
					
					// Create colors
					CGColorRef borderColor = CGColorCreateGenericRGB(0.67f, 0.67f, 0.67f, 1.f);
					CGColorRef rowBG = CGColorCreateGenericRGB(1.f, 1.f, 1.f, 1.f);
					CGColorRef altRowBG = CGColorCreateGenericRGB(0.9f, 0.9f, 0.9f, 1.f);
					
					CGFloat borderWidth = 1.f;
					
					// We use NSGraphicsContext for the strings due to easier string drawing :P
					NSGraphicsContext *nsContext = [NSGraphicsContext graphicsContextWithGraphicsPort:(void *)context flipped:YES];
					[NSGraphicsContext setCurrentContext:nsContext];
					if (nil != nsContext) {
						NSFont *myFont = [NSFont systemFontOfSize:fontSize];
						NSColor *rowTextColor = [NSColor colorWithCalibratedWhite:0.25f alpha:1.f];
						NSDictionary *stringAttributes = @{NSFontAttributeName: myFont,
														  NSForegroundColorAttributeName: rowTextColor};
						
						CGFloat textXPadding = 5.f;
						CGFloat cellX = 0.f;
						CGFloat maxCellStringWidth;
						
						// loop each column
						for (NSString *colKey in csvDoc.columnKeys) {
							if (cellX > maxBounds.size.width) {
								break;
							}
							
							CGRect rowRect = CGRectMake(cellX, 0.f, maxBounds.size.width - cellX, rowHeight);
							maxCellStringWidth = 0.f;
							BOOL isFirstColumn = [csvDoc isFirstColumn:colKey];
							BOOL altRow = NO;
							
							// loop rows of this column
							for (CSVRowObject *row in csvDoc.rows) {
								
								// Draw background
								if (isFirstColumn) {
									CGContextSetFillColorWithColor(context, altRow ? altRowBG : rowBG);
									CGContextFillRect(context, rowRect);
								}
								
								// Draw border
								else {
									CGContextMoveToPoint(context, cellX + borderWidth / 2, rowRect.origin.y);
									CGContextAddLineToPoint(context, cellX + borderWidth / 2, rowRect.origin.y + rowRect.size.height);
									CGContextSetStrokeColorWithColor(context, borderColor);
									CGContextStrokePath(context);
								}
								
								// Draw text
								NSRect textRect = NSRectFromCGRect(rowRect);
								textRect.size.width -= 2 * textXPadding;
								textRect.origin.x += textXPadding;
								NSString *cellString = [row columnForKey:colKey];
								NSSize cellSize = [cellString sizeWithAttributes:stringAttributes];
								[cellString drawWithRect:textRect options:NSStringDrawingUsesLineFragmentOrigin attributes:stringAttributes];
								
								if (cellSize.width > maxCellStringWidth) {
									maxCellStringWidth = cellSize.width;
								}
								altRow = !altRow;
								rowRect.origin.y += rowHeight;
								
								// adjust usedBounds
								if (usedBounds.size.height < rowRect.origin.y) {
									usedBounds.size.height = rowRect.origin.y;
								}
							}
							
							cellX += maxCellStringWidth + 2 * textXPadding;
							usedBounds.size.width = cellX;
						}
						
						// adjust the bounds to respect our fixed aspect ratio - portrait
						//NSLog(@"%@  is: %.2fx%.2f  -- max: %.2fx%.2f", myURL, usedBounds.size.width, usedBounds.size.height, maxBounds.size.width, maxBounds.size.height);
						if ((usedBounds.size.width > maxBounds.size.width && usedBounds.size.height > maxBounds.size.height)
							|| (usedBounds.size.width <= usedBounds.size.height)) {
							badgeMaxSize = usedBounds.size.height;
							usedBounds.size.width = usedBounds.size.height * ASPECT;
						}
						
						// landscape
						else {
							badgeMaxSize = usedBounds.size.width;
							
							CGFloat my_height = usedBounds.size.width * ASPECT;
							if (usedBounds.size.height < my_height) {
								CGRect missingRect = CGRectMake(0.f, usedBounds.size.height, ceilf(usedBounds.size.width), ceilf(my_height - usedBounds.size.height));
								CGContextSetFillColorWithColor(context, rowBG);
								CGContextFillRect(context, missingRect);
							}
							usedBounds.size.height = my_height;
						}
					}
					
					//CGPDFContextEndPage(context);
					
					CGColorRelease(borderColor);
					CGColorRelease(rowBG);
					CGColorRelease(altRowBG);
					
					// Create a CGImage
					CGImageRef fullImage = CGBitmapContextCreateImage(context);
					CGImageRef usedImage = CGImageCreateWithImageInRect(fullImage, usedBounds);
					CGImageRelease(fullImage);
					
					// Draw the image to the thumbnail request
					CGContextRef thumbContext = QLThumbnailRequestCreateContext(thumbnail, usedBounds.size, false, NULL);
					CGContextDrawImage(thumbContext, usedBounds, usedImage);
					CGImageRelease(usedImage);
					
					// we no longer need the bitmap data; free (malloc'ed by createRGBABitmapContext() )
					char *contextData = CGBitmapContextGetData(context);
					if (contextData) {
						free(contextData);
					}
					
					// Draw the CSV badge to the icon
					NSGraphicsContext *thumbNsContext = [NSGraphicsContext graphicsContextWithGraphicsPort:(void *)thumbContext flipped:NO];
					[NSGraphicsContext setCurrentContext:thumbNsContext];
					if (nil != thumbNsContext) {
						NSString *badgeString = [@"	" isEqualToString:csvDoc.separator] ? BADGE_TSV : BADGE_CSV;
						CGFloat badgeFontSize = ceilf(badgeMaxSize * 0.28f);
						NSFont *badgeFont = [NSFont boldSystemFontOfSize:badgeFontSize];
						NSColor *badgeColor = [NSColor colorWithCalibratedRed:0.05f green:0.25f blue:0.1f alpha:1.f];
						NSShadow *badgeShadow = [NSShadow new];
						[badgeShadow setShadowOffset:NSMakeSize(0.f, 0.f)];
						[badgeShadow setShadowBlurRadius:badgeFontSize * 0.01f];
						[badgeShadow setShadowColor:[NSColor whiteColor]];
						
						// Set attributes and draw
						NSDictionary *badgeAttributes = @{NSFontAttributeName: badgeFont,
														 NSForegroundColorAttributeName: badgeColor,
														 NSShadowAttributeName: badgeShadow};
						
						NSSize badgeSize = [badgeString sizeWithAttributes:badgeAttributes];
						CGFloat badge_x = (usedBounds.size.width / 2) - (badgeSize.width / 2);
						CGFloat badge_y = 0.025f * badgeMaxSize;
						NSRect badgeRect = NSMakeRect(badge_x, badge_y, 0.f, 0.f);
						badgeRect.size = badgeSize;
						
						[badgeString drawWithRect:badgeRect options:NSStringDrawingUsesLineFragmentOrigin attributes:badgeAttributes];
					}
					
					
					// Clean up
					QLThumbnailRequestFlushContext(thumbnail, thumbContext);
					CGContextRelease(thumbContext);
					CGContextRelease(context);
				}
			}
		}
	}
	
	return noErr;
}

void CancelThumbnailGeneration(void* thisInterface, QLThumbnailRequestRef thumbnail)
{
}



#pragma mark - Creating a bitmap context
static CGContextRef createRGBABitmapContext(CGSize pixelSize)
{
	NSUInteger width = pixelSize.width;
	NSUInteger height = pixelSize.height;
	NSUInteger bitmapBytesPerRow = width * 4;				// 1 byte per component r g b a
	NSUInteger bitmapBytes = bitmapBytesPerRow * height;
	
	// allocate needed bytes
	void *bitmapData = malloc(bitmapBytes);
	if (NULL == bitmapData) {
		fprintf(stderr, "Oops, could not allocate bitmap data!");
		return NULL;
	}
	
	// create the context
	CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
	CGContextRef context = CGBitmapContextCreate(bitmapData, width, height, 8, bitmapBytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast);
	CGColorSpaceRelease(colorSpace);
	
	// context creation fail
	if (NULL == context) {
		free(bitmapData);
		fprintf(stderr, "Oops, could not create the context!");
		return NULL;
	}
	
	return context;
}

/*
static CGContextRef createVectorContext(CGSize pixelSize)
{
	CGRect mediaBox = CGRectMake(0.f, 0.f, 0.f, 0.f);
	mediaBox.size = pixelSize;
	
	// allocate needed bytes
	CFMutableDataRef data = CFDataCreateMutable(kCFAllocatorDefault, 0);		// unlimited size; hopefully we won't regret this :)
	if (NULL == bitmapData) {
		fprintf(stderr, "Oops, could not allocate mutable data!");
		return NULL;
	}
	
	// create the context
	CGDataConsumerRef consumer = CGDataConsumerCreateWithCFData(data);
	CGContextRef context = CGPDFContextCreate(consumer, &mediaBox, NULL);	
	CGDataConsumerRelease(consumer);
	
	// context creation fail
	if (NULL == context) {
		free(bitmapData);
		fprintf(stderr, "Oops, could not create the context!");
		return NULL;
	}
	
	return context;
	
	
	// Don't forget creating pages
	// CGPDFContextBeginPage(pdfContext, NULL);
	// CGPDFContextEndPage(pdfContext);
	
	// and release the data
	// CFRelease(data);
}	//	*/