RE: cairo drawing problem

Hi Andreas,

My first instinct is ‘are you releasing some internal object loaned to you, which you never retained’.

My cleanup didn’t reveal anything particular, but:

NSBitmapImageRep *rep = [[NSBitmapImageRep alloc] initWithFocusedViewRect:[mapView bounds]];

NSDictionary * props = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:1]

forKey:@"NSImageInterlaced"];

NSData * repData = [rep representationUsingType:NSPNGFileType

properties:props]

NSData * data = "" retain] autorelease];

Note that the autoreleased repData is retained and then autoreleased (meaning the same object is put onto the autorelease queue twice)

Then I saw the rest of the code you attached. My thought goes in the direction of ‘_sharedMapView’-related code. Even though you’re allocating a whole new window only when the map view is not shared, you seem to be releasing window unconditionally.

Based on the output, I’m concluding you are running with _sharedMapView==NO and thus releasing the mapview and window incorrectly which possibly results in an X drawable being destroyed while still in use.

Some suggestions:

- start the program with GDB and put a breakpoint on the lines mentioning “X-Window error” in libs-back?

- In the current code, I found these in only one file: https://github.com/gnustep/libs-back/blob/2a0e305a4f3ec93c00a96a13838877c9543449a9/Source/x11/XGServerEvent.m line 206 and 216. Based on the output, I’d expect it’s enough to put it on line 206 (the NSLog instead of the NSException).

- split up the function: while there may be valid reasons to have really long functions, this is not one of them and it’s hard to read and understand what’s going on

- if you had a “draw into view” function (which should really be implemented inside the mapview class itself), separate from window allocation and release (or use of shared window and mapview), you’d have spotted that the alloc/new/retain/release don’t match

- provide a truly minimal example

- if you would cut out everything that actually does the drawing, create a new project, and slowly move in the drawing code into this PNG export function, you’d more easily notice the problems

Ivan Vučica

From: Fred Kiefer
Sent: Thursday 11 June 2020 22:57
To: Andreas Höschler
Cc: GNUstep Discuss
Subject: Re: cairo drawing problem

Hi Andreas,

I did not get your original mail and it isn’t even in my spam folder where your previous mails.

> Am 11.06.2020 um 00:05 schrieb Josh Freeman <gnustep_lists@twilightedge.com>:

> Try initializing your window as NSBackingStoreBuffered? (NSBackingStoreNonretained tells the window to draw directly to the screen without buffering, so the pixel data is probably unavailable for reading back).

This might help but I really would like to understand where the issue comes from in the first place.

Looking at the code and the output below the first thing I notice is that the X error happens after the extraction of the view data into the bitmap image was finished. The most likely scenario is that the data we extracted is somehow invalid. That would fit in wit your suggested work around.

But all of this is just blind guessing, what we need here is example code that allows to reproduce this issue with GNUstep classes only.

Andreas, could you please strip down your application to pure GNUstep and if that still displays the error send out that code?

Cheers,

Fred

> On Jun 8, 2020, at 1:52 PM, Andreas Höschler via Discussion list for the GNUstep programming environment wrote:

>> Hi all,

>> I have just found some time to continue testing my app(s) on GNUstep and realised that drawing OSM maps fails under GNUstep when using the cairo backend while it works if using libart.

>> My code draws something in a NSView subclass and then uses

>> [mapView display];

>> [mapView lockFocus];

>> NSBitmapImageRep *rep = [[NSBitmapImageRep alloc] initWithFocusedViewRect:[mapView bounds]];

>> data = "" representationUsingType:NSPNGFileType properties:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:1] forKey:@"NSImageInterlaced"]] retain] autorelease];

>> if ([data length] == 0) // try TIFF instead

>> {

>> data = "" representationUsingType:NSTIFFFileType properties:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:1] forKey:@"NSImageInterlaced"]] retain] autorelease];

>> if ([data length] == 0) NSLog(@"Damn! TIFF failed as well!");

>> }

>> [mapView unlockFocus];

>> to produce a PNG from the view content. This works great with libart

>> art:

>> ============================================================================

>> 2020-06-08 19:37:18.526 ESMMapServer[10165:10165] draw way inlays... 359 _drawPrimaryInLays 1 _drawOtherInLays 1

>> 2020-06-08 19:37:18.527 ESMMapServer[10165:10165] BUMM

>> 2020-06-08 19:37:18.545 ESMMapServer[10165:10165] Draw 7 mapShields ...

>> 2020-06-08 19:37:18.548 ESMMapServer[10165:10165] Draw 1 mapLocs ...

>> 2020-06-08 19:37:18.549 ESMMapServer[10165:10165] Draw 2 mapLines ...

>> 2020-06-08 19:37:18.549 ESMMapServer[10165:10165] <ESMMapLine: 0x2ed0550> drawLine _colorName (null) _color 0 0 1

>> 2020-06-08 19:37:18.549 ESMMapServer[10165:10165] <ESMMapLine: 0x2ed4610> drawLine _colorName (null) _color 0 1 0

>> 2020-06-08 19:37:18.557 ESMMapServer[10165:10165] h=--- v=--- <ESMMapView: 0x2302ca0> f={x = 0; y = 0; width = 542; height = 620} b={x = 0; y = 0; width = 542; height = 620} locking Focus ..

>> 2020-06-08 19:37:18.557 ESMMapServer[10165:10165] getting rep ...

>> 2020-06-08 19:37:18.563 ESMMapServer[10165:10165] rep <NSBitmapImageRep: 0x2f15450 size: {width = 542; height = 620} pixelsWide: 542 pixelsHigh: 620 colorSpaceName: NSDeviceRGBColorSpace bps: 8>

>> 2020-06-08 19:37:18.665 ESMMapServer[10165:10165] h=--- v=--- <ESMMapView: 0x2302ca0> f={x = 0; y = 0; width = 542; height = 620} b={x = 0; y = 0; width = 542; height = 620} unocked Focus!

>> 2020-06-08 19:37:18.665 ESMMapServer[10165:10165] data 248529

>> but fails with cairo

>> cairo:

>> =======================================================================================

>> 2020-06-08 19:31:52.783 ESMMapServer[9982:9982] draw way inlays... 359 _drawPrimaryInLays 1 _drawOtherInLays 1

>> 2020-06-08 19:31:52.783 ESMMapServer[9982:9982] BUMM

>> 2020-06-08 19:31:52.798 ESMMapServer[9982:9982] Draw 8 mapShields ...

>> 2020-06-08 19:31:52.801 ESMMapServer[9982:9982] Draw 1 mapLocs ...

>> 2020-06-08 19:31:52.802 ESMMapServer[9982:9982] Draw 2 mapLines ...

>> 2020-06-08 19:31:52.802 ESMMapServer[9982:9982] <ESMMapLine: 0x33b52c0> drawLine _colorName (null) _color 0 0 1

>> 2020-06-08 19:31:52.802 ESMMapServer[9982:9982] <ESMMapLine: 0x33c3d30> drawLine _colorName (null) _color 0 1 0

>> 2020-06-08 19:31:52.811 ESMMapServer[9982:9982] h=--- v=--- <ESMMapView: 0x28e0fe0> f={x = 0; y = 0; width = 542; height = 620} b={x = 0; y = 0; width = 542; height = 620} locking Focus ...

>> 2020-06-08 19:31:52.812 ESMMapServer[9982:9982] getting rep ...

>> 2020-06-08 19:31:52.815 ESMMapServer[9982:9982] rep <NSBitmapImageRep: 0x3698ef0 size: {width = 542; height = 620} pixelsWide: 542 pixelsHigh: 620 colorSpaceName: NSDeviceRGBColorSpace bps: 8>

>> 2020-06-08 19:31:52.882 ESMMapServer[9982:9982] h=--- v=--- <ESMMapView: 0x28e0fe0> f={x = 0; y = 0; width = 542; height = 620} b={x = 0; y = 0; width = 542; height = 620} unocked Focus!

>> 2020-06-08 19:31:52.883 ESMMapServer[9982:9982] data 1383

>> 2020-06-08 19:31:52.921 ESMMapServer[9982:9982] X-Windows error - RenderBadPicture (invalid Picture parameter)

>> on display: :0

>> type: 0

>> serial number: 1169

>> request code: 139

>> data contains nothing reasonable after this X-WIndows error. I have attached the complete implementation of

>> - (NSDictionary *)PNGForMapRequestDic:(NSDictionary *)dic;

>> for reference below (contains the lockFocus ... unlockFocus magic). Any idea what might be causing this X-Windows error with cairo? I am stuck when it gets to backend issues. I might have to add that this error occurs in a tool (no gui app) named ESMMapServer which is supposed to produce maps (PNGs) from OSM data in the background.

>> Thanks a lot,

>> Andreas

>> - (NSDictionary *)PNGForMapRequestDic:(NSDictionary *)dic

>> {

>> NSNumber *pixelWidth = [dic objectForKey:@"pixelWidth"];

>> NSNumber *pixelHeight = [dic objectForKey:@"pixelHeight"];

>> NSNumber *x = [dic objectForKey:@"x"];

>> NSNumber *y = [dic objectForKey:@"y"];

>> NSNumber *width = [dic objectForKey:@"width"];

>> NSNumber *height = [dic objectForKey:@"height"];

>> NSArray *locations = [dic objectForKey:@"locations"];

>> NSArray *hintPaths = [dic objectForKey:@"hintPaths"];

>> BOOL drawTextMarks = [[dic objectForKey:@"drawTextMarks"] intValue];

>> NSLog(@"PNGForMapRequestDic hintPaths %d %@ %@ %@ %@ pixelWidth %@ pixelHeight %@", [hintPaths count], x, y, width, height, pixelWidth, pixelHeight);

>> NSLog(@"locations %@", [locations description]);

>> [_shields removeAllObjects];

>> if ((pixelWidth) && (pixelHeight) && (x) && (y) && (width) && (height))

>> {

>> _visibleMapSection = NSMakeRect ([x floatValue], [y floatValue], [width floatValue], [height floatValue]);

>> if (_visibleMapSection.size.height > MAXESMMAPHEIGHT) // reducing map size to avoid OSMMapServer break down <-----------

>> {

>> NSLog(@"reducing map size to avoid OSMMapServer break down %f -> %f", _visibleMapSection.size.height, MAXESMMAPHEIGHT);

>> float margin = (_visibleMapSection.size.height - MAXESMMAPHEIGHT) / 2;

>> _visibleMapSection.origin.y += margin;

>> _visibleMapSection.size.height = MAXESMMAPHEIGHT;

>> }

>> _imageSize = NSMakeSize([pixelWidth floatValue], [pixelHeight floatValue]);

>> NSLog(@"_imageSize %@", NSStringFromSize(_imageSize));

>> if (_imageSize.width / _imageSize.height > (_visibleMapSection.size.width * cos ((_visibleMapSection.origin.y + _visibleMapSection.size.height / 2.0) / 180.0 * 3.14)) / _visibleMapSection.size.height)

>> {

>> float correctedWidth = _visibleMapSection.size.height * _imageSize.width / (_imageSize.height * cos ((_visibleMapSection.origin.y + _visibleMapSection.size.height / 2.0) / 180.0 * 3.14));

>> // NSLog(@"requested width %f correctedWidth %f", _visibleMapSection.size.width, correctedWidth);

>> _visibleMapSection.origin.x -= (correctedWidth - _visibleMapSection.size.width) / 2.0;

>> _visibleMapSection.size.width = correctedWidth;

>> }

>> else

>> {

>> float correctedHeight = (_visibleMapSection.size.width * _imageSize.height * cos ((_visibleMapSection.origin.y + _visibleMapSection.size.height / 2.0) / 180.0 * 3.14) / _imageSize.width);

>> // NSLog(@"requested height %f correctedHeight %f", _visibleMapSection.size.height, correctedHeight);

>> _visibleMapSection.origin.y -= (correctedHeight - _visibleMapSection.size.height) / 2.0;

>> _visibleMapSection.size.height = correctedHeight;

>> }

>> NSLog(@"_visibleMapSection %@", NSStringFromRect(_visibleMapSection));

>> NSArray *presentations = [self suitablePresentationsForRect:_visibleMapSection];

>> // NSLog(@"presentations %@", [presentations description]);

>> NSEnumerator *enumerator = [presentations objectEnumerator];

>> ESMMapPresentation *presentation;

>> NSArray *highways = nil;

>> NSArray *ways = nil;

>> NSArray *namedNodes = nil;

>> ESMMapView *mapView = nil;

>> NSWindow *window = nil;

>> NSLog(@"_sharedMapView %@", _sharedMapView);

>> if (_sharedMapView)

>> {

>> mapView = (ESMMapView *)[_sharedMapView retain];

>> [mapView removeAllPathsAndMapLabels];

>> }

>> else

>> {

>> window = [[NSWindow alloc] initWithContentRect:NSMakeRect(0,0, _imageSize.width, _imageSize.height) styleMask:NSBorderlessWindowMask backing:NSBackingStoreNonretained defer:NO];

>> mapView = [[ESMMapView alloc] initWithFrame:NSMakeRect(0, 0, _imageSize.width, _imageSize.height)];

>> NSData *data = "">

>> if (_sharedMapView)

>> {

>> [mapView prepareOSMDrawing];

>> NSLog(@"%@ calling display ..", mapView);

>> [mapView display];

>> NSLog(@"%@ display done", mapView);

>> }

>> else

>> {

>> [mapView display];

>> NS_DURING

>> NSLog(@"%@ locking Focus ...", mapView);

>> [mapView lockFocus];

>> NSLog(@"getting rep ...");

>> // NSLog(@"window frame %@", NSStringFromRect([[mapView window] frame]));

>> // NSLog(@"contentView frame %@", NSStringFromRect([[[mapView window] contentView] frame]));

>> // NSLog(@"frame %@", NSStringFromRect([mapView frame]));

>> // NSLog(@"bounds %@", NSStringFromRect([mapView bounds]));

>> NSBitmapImageRep *rep = [[NSBitmapImageRep alloc] initWithFocusedViewRect:[mapView bounds]];

>> NSLog(@"rep %@", rep);

>> data = "" representationUsingType:NSPNGFileType properties:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:1] forKey:@"NSImageInterlaced"]] retain] autorelease];

>> /* {

>> NSString *path = @"/home/ahoesch/A.tiff";

>> NSData *data = "" representationUsingType:NSTIFFFileType properties:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:1] forKey:@"NSImageInterlaced"]] retain] autorelease];

>> [data writeToFile:path atomically:YES];

>> }

>> */

>> if ([data length] == 0) // try TIFF instead

>> {

>> NSLog(@"Getting PNG data failed! We try TIFF instead ...");

>> // NSData *data = "" TIFFRepresentation] retain] autorelease];

>> data = "" representationUsingType:NSTIFFFileType properties:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:1] forKey:@"NSImageInterlaced"]] retain] autorelease];

>> if ([data length] == 0) NSLog(@"Damn! TIFF failed as well!");

>> }

>> [mapView unlockFocus];

>> NSLog(@"%@ unocked Focus!", mapView);

>> [rep release];

>> NS_HANDLER

>> NSLog(@"Something went terribly wrong: %@", [localException description]);

>> // NSView *clipView = [mapView superview];

>> // NSLog(@"clipView %@ bounds %@", NSStringFromRect([clipView frame]), NSStringFromRect([clipView bounds]));

>> NS_ENDHANDLER

>> }

>> NSLog(@"data %d", [data length]);

>> [window release];

>> [mapView release];

>> return [NSDictionary dictionaryWithObjectsAndKeys:

>> [NSNumber numberWithFloat:_visibleMapSection.origin.x], @"visibleMapSection.origin.x",

>> [NSNumber numberWithFloat:_visibleMapSection.origin.y], @"visibleMapSection.origin.y",

>> [NSNumber numberWithFloat:_visibleMapSection.size.width], @"visibleMapSection.size.width",

>> [NSNumber numberWithFloat:_visibleMapSection.size.height], @"visibleMapSection.size.height",

>> data, @"imageData",

>> nil];

>> }

>> else return nil;

>> }

From:	Ivan Vučica
Subject:	RE: cairo drawing problem
Date:	Fri, 12 Jun 2020 18:43:47 +0100