Re: Drawing after CGContextClosePath() still appends line
may be you can try CGContextSaveState and CGContextRestoreState ~~ 在 2013年8月20日，上午8:03，Rick Mann rm...@latencyzero.com 写道： I'm drawing a couple of arcs and then calling ClosePath() to close up the shape I drew. This works great. But then I repeat the process in a different place, and stroke the whole thing. Unfortunately, Core Graphics adds a line from the last point in the closed path to the first point of the new arc I add. From my reading of the docs, this line shouldn't happen. After closing the subpath, your application can begin a new subpath without first calling CGContextMoveToPoint. In this case, a new subpath is implicitly created with a starting and current point equal to the previous subpath’s starting point. Now, the AddArc() docs do say it might be preceded by a straight line segment, but when the context first starts, there is no starting position; I wonder why the subpath doesn't behave the same way after ClosePath(). iOS 6.1.3, iPad simulator or device. -- Rick ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/zoutian62%40icloud.com This email sent to zoutia...@icloud.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Drawing after CGContextClosePath() still appends line
On 20/08/2013, at 2:51 AM, Rick Mann rm...@latencyzero.com wrote: Obviously, it can't be changed now, but AddArc() should never have drawn that first line segment. It's inconsistent with what you probably want, and with other methods like CGContextAddLines() or CGContextAddRect(). Depends. In some cases it's really handy that it adds the line - e.g. for drawing round-cornered rectangles where calculating the actual end point of the arc is tedious - instead just use a centre point and radius and it figures out the rest for you. I guess the engineer decided that these useful cases outweigh those other cases when it's a nuisance. --Graham ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Drawing after CGContextClosePath() still appends line
On Aug 19, 2013, at 6:08 PM, zou tian zoutia...@icloud.com wrote: may be you can try CGContextSaveState and CGContextRestoreState ~~ These functions don’t save and restore the current path. -- David Duncan ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Drawing after CGContextClosePath() still appends line
I'm drawing a couple of arcs and then calling ClosePath() to close up the shape I drew. This works great. But then I repeat the process in a different place, and stroke the whole thing. Unfortunately, Core Graphics adds a line from the last point in the closed path to the first point of the new arc I add. From my reading of the docs, this line shouldn't happen. After closing the subpath, your application can begin a new subpath without first calling CGContextMoveToPoint. In this case, a new subpath is implicitly created with a starting and current point equal to the previous subpath’s starting point. Now, the AddArc() docs do say it might be preceded by a straight line segment, but when the context first starts, there is no starting position; I wonder why the subpath doesn't behave the same way after ClosePath(). iOS 6.1.3, iPad simulator or device. -- Rick ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Drawing after CGContextClosePath() still appends line
On 20 Aug, 2013, at 8:03 AM, Rick Mann rm...@latencyzero.com wrote: I'm drawing a couple of arcs and then calling ClosePath() to close up the shape I drew. This works great. But then I repeat the process in a different place, and stroke the whole thing. Unfortunately, Core Graphics adds a line from the last point in the closed path to the first point of the new arc I add. From my reading of the docs, this line shouldn't happen. After closing the subpath, your application can begin a new subpath without first calling CGContextMoveToPoint. In this case, a new subpath is implicitly created with a starting and current point equal to the previous subpath’s starting point. From my reading that's exactly what should happen. You close the subpath then you implicitly start one because you didn't call CGContextMoveToPoint() when you add the next arc, that path starts from the original starting point of the old subpath (which is functionally exactly the same as the endpoint). So the new subpath starts with a line to the start of your new arc from the start of the previous path. If you don't want that, do the move. There's a difference between a context with no path at all and a context which already contains subpaths, closed or not. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Drawing after CGContextClosePath() still appends line
On Aug 19, 2013, at 17:25 , Roland King r...@rols.org wrote: On 20 Aug, 2013, at 8:03 AM, Rick Mann rm...@latencyzero.com wrote: I'm drawing a couple of arcs and then calling ClosePath() to close up the shape I drew. This works great. But then I repeat the process in a different place, and stroke the whole thing. Unfortunately, Core Graphics adds a line from the last point in the closed path to the first point of the new arc I add. From my reading of the docs, this line shouldn't happen. After closing the subpath, your application can begin a new subpath without first calling CGContextMoveToPoint. In this case, a new subpath is implicitly created with a starting and current point equal to the previous subpath’s starting point. From my reading that's exactly what should happen. You close the subpath then you implicitly start one because you didn't call CGContextMoveToPoint() when you add the next arc, that path starts from the original starting point of the old subpath (which is functionally exactly the same as the endpoint). So the new subpath starts with a line to the start of your new arc from the start of the previous path. If you don't want that, do the move. There's a difference between a context with no path at all and a context which already contains subpaths, closed or not. Oh, I think you're right. Pity. It makes working with arcs a real pain. I have to compute the arc's starting point and move to it. Unless I'm missing something? -- Rick ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Drawing after CGContextClosePath() still appends line
On 20 Aug, 2013, at 8:36 AM, Rick Mann rm...@latencyzero.com wrote: On Aug 19, 2013, at 17:25 , Roland King r...@rols.org wrote: On 20 Aug, 2013, at 8:03 AM, Rick Mann rm...@latencyzero.com wrote: I'm drawing a couple of arcs and then calling ClosePath() to close up the shape I drew. This works great. But then I repeat the process in a different place, and stroke the whole thing. Unfortunately, Core Graphics adds a line from the last point in the closed path to the first point of the new arc I add. From my reading of the docs, this line shouldn't happen. After closing the subpath, your application can begin a new subpath without first calling CGContextMoveToPoint. In this case, a new subpath is implicitly created with a starting and current point equal to the previous subpath’s starting point. From my reading that's exactly what should happen. You close the subpath then you implicitly start one because you didn't call CGContextMoveToPoint() when you add the next arc, that path starts from the original starting point of the old subpath (which is functionally exactly the same as the endpoint). So the new subpath starts with a line to the start of your new arc from the start of the previous path. If you don't want that, do the move. There's a difference between a context with no path at all and a context which already contains subpaths, closed or not. Oh, I think you're right. Pity. It makes working with arcs a real pain. I have to compute the arc's starting point and move to it. Unless I'm missing something? So many ways to attack that. Stroke the segments one-by-one. Or instead of going right to the context, create a CGMutablePathRef() for each arc , draw to that, then add it to the context path. Heck if you are drawing the same shape each time you can even reuse the path and change the CTM to move it around when you add then then you only even have to draw it once. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Drawing after CGContextClosePath() still appends line
On Aug 19, 2013, at 7:36 PM, Rick Mann wrote: On Aug 19, 2013, at 17:25 , Roland King r...@rols.org wrote: On 20 Aug, 2013, at 8:03 AM, Rick Mann rm...@latencyzero.com wrote: I'm drawing a couple of arcs and then calling ClosePath() to close up the shape I drew. This works great. But then I repeat the process in a different place, and stroke the whole thing. Unfortunately, Core Graphics adds a line from the last point in the closed path to the first point of the new arc I add. From my reading of the docs, this line shouldn't happen. After closing the subpath, your application can begin a new subpath without first calling CGContextMoveToPoint. In this case, a new subpath is implicitly created with a starting and current point equal to the previous subpath’s starting point. From my reading that's exactly what should happen. You close the subpath then you implicitly start one because you didn't call CGContextMoveToPoint() when you add the next arc, that path starts from the original starting point of the old subpath (which is functionally exactly the same as the endpoint). So the new subpath starts with a line to the start of your new arc from the start of the previous path. If you don't want that, do the move. There's a difference between a context with no path at all and a context which already contains subpaths, closed or not. Oh, I think you're right. Pity. It makes working with arcs a real pain. I have to compute the arc's starting point and move to it. Unless I'm missing something? You can begin a new path for each arc. If you ultimately want one path with multiple disjoint subpaths, I think you can create the arc subpaths as individual CGPath objects and add them to either the context path or to a master CGPath object. Regards, Ken ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Drawing after CGContextClosePath() still appends line
On Aug 19, 2013, at 17:47 , Ken Thomases k...@codeweavers.com wrote: On Aug 19, 2013, at 7:36 PM, Rick Mann wrote: On Aug 19, 2013, at 17:25 , Roland King r...@rols.org wrote: On 20 Aug, 2013, at 8:03 AM, Rick Mann rm...@latencyzero.com wrote: I'm drawing a couple of arcs and then calling ClosePath() to close up the shape I drew. This works great. But then I repeat the process in a different place, and stroke the whole thing. Unfortunately, Core Graphics adds a line from the last point in the closed path to the first point of the new arc I add. From my reading of the docs, this line shouldn't happen. After closing the subpath, your application can begin a new subpath without first calling CGContextMoveToPoint. In this case, a new subpath is implicitly created with a starting and current point equal to the previous subpath’s starting point. From my reading that's exactly what should happen. You close the subpath then you implicitly start one because you didn't call CGContextMoveToPoint() when you add the next arc, that path starts from the original starting point of the old subpath (which is functionally exactly the same as the endpoint). So the new subpath starts with a line to the start of your new arc from the start of the previous path. If you don't want that, do the move. There's a difference between a context with no path at all and a context which already contains subpaths, closed or not. Oh, I think you're right. Pity. It makes working with arcs a real pain. I have to compute the arc's starting point and move to it. Unless I'm missing something? You can begin a new path for each arc. If you ultimately want one path with multiple disjoint subpaths, I think you can create the arc subpaths as individual CGPath objects and add them to either the context path or to a master CGPath object. This is basically what I'm doing now. Obviously, it can't be changed now, but AddArc() should never have drawn that first line segment. It's inconsistent with what you probably want, and with other methods like CGContextAddLines() or CGContextAddRect(). -- Rick ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
