BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  how to detech mouse coordinates X and Y in dblclick event Goto page 1, 2  Next          BorlandTalk.com Forum Index -> C++ Builder (VCL Components Usage) View previous topic :: View next topic   Author Message Sreekanth Reddy Bandi Guest Posted: Wed Apr 28, 2004 10:37 am    Post subject: how to detech mouse coordinates X and Y in dblclick event Hi, Can you help me how to detect mouse co-ordinates X, Y where dblclick event is happened on a form? Many Thanks in advance, Sreekanth Back to top Andrue Cope Guest Posted: Wed Apr 28, 2004 10:52 am    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even On Wed, 28 Apr 2004 16:07:43 +0530, Sreekanth Reddy Bandi wrote: Quote: Can you help me how to detect mouse co-ordinates X, Y where dblclick event is happened on a form? Make a note of them in OnMouseUp. -- Andrue Cope [Bicester UK] Back to top Hans Galema Guest Posted: Wed Apr 28, 2004 10:58 am    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even Sreekanth Reddy Bandi wrote: Quote: Can you help me how to detect mouse co-ordinates X, Y where dblclick event is happened on a form? There are several ways. You can use the GetCursorPos function and convert the coordinates to the form coordinates. You could also take two private variables int Xpos; int Ypos; and in the MouseDown eventhandler (which has the X and Y as parameters, and always comes before the DoubleClick event) assign X and Y to Xpos resp. Ypos. Then in the OnDoubleclick eventhandler use Xpos and Ypos. Hans. Quote: Many Thanks in advance, ? Hans. Back to top Remy Lebeau (TeamB) Guest Posted: Wed Apr 28, 2004 5:40 pm    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even "Sreekanth Reddy Bandi" <sreekanth_reddy (AT) persistent (DOT) co.in> wrote Quote: Can you help me how to detect mouse co-ordinates X, Y where dblclick event is happened on a form? You will have to use the GetCursorPos() function from the Win32 API, or the global TMouse::CursorPos property from the VCL (older versions of the VCL don't have a global TMouse object). Once you have the coordinates of the mouse cursor on the screen, you can translate them into client coordinates by using the form's ScreenToClient() method. Gamit Back to top Corey Murtagh Guest Posted: Wed Apr 28, 2004 8:03 pm    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even Remy Lebeau (TeamB) wrote: Quote: "Sreekanth Reddy Bandi" <sreekanth_reddy (AT) persistent (DOT) co.in> wrote in message news:408f897a (AT) newsgroups (DOT) borland.com... Can you help me how to detect mouse co-ordinates X, Y where dblclick event is happened on a form? You will have to use the GetCursorPos() function from the Win32 API, or the global TMouse::CursorPos property from the VCL (older versions of the VCL don't have a global TMouse object). Once you have the coordinates of the mouse cursor on the screen, you can translate them into client coordinates by using the form's ScreenToClient() method. GetCursorPos() will return the /current/ location of the mouse cursor, which may be completely unrelated to its position at the time the double-click event was generated. Only way to be sure is to save the cursor position at the time of the event... MouseDown or MouseUp. -- Corey Murtagh The Electric Monk "Quidquid latine dictum sit, altum viditur!" Back to top Remy Lebeau (TeamB) Guest Posted: Wed Apr 28, 2004 8:24 pm    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even "Corey Murtagh" <emonk (AT) slingshot (DOT) no.uce> wrote Quote: GetCursorPos() will return the /current/ location of the mouse cursor, which may be completely unrelated to its position at the time the double-click event was generated. Possibly, but only if message handling is delayed. If you are not blocking the main VCL thread, then the coordinates will match (to within a few pixels, anyway). Quote: Only way to be sure is to save the cursor position at the time of the event... MouseDown or MouseUp. Actually, since OnDblClick is triggered in the context of a WM_LBUTTONDBLCLK message, you could try calling GetMessagePos(), which will return the actual cordinates of the mouse cursor at the time the message was first issued. Of course, if the VCL is simulating that message at any time, GetMessagePos() is useless. It will only work for messages retrieved from the main message queue itself. But it is an alternative to consider. Gambit Back to top Hans Galema Guest Posted: Wed Apr 28, 2004 8:34 pm    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even Corey Murtagh wrote: Quote: GetCursorPos() will return the /current/ location of the mouse cursor, which may be completely unrelated to its position at the time the double-click event was generated. Only way to be sure is to save the cursor position at the time of the event... MouseDown or MouseUp. Sorry, that makes no sense. The MouseUp and MousDown events are also on a different time then the OnDoubleClick even. Every solution will have the same problem. Of course GetCursorpos should be called as first statement in the OnDblClick eventhandler. Hans. Back to top Corey Murtagh Guest Posted: Wed Apr 28, 2004 9:04 pm    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even Hans Galema wrote: Quote: Corey Murtagh wrote: GetCursorPos() will return the /current/ location of the mouse cursor, which may be completely unrelated to its position at the time the double-click event was generated. Only way to be sure is to save the cursor position at the time of the event... MouseDown or MouseUp. Sorry, that makes no sense. The MouseUp and MousDown events are also on a different time then the OnDoubleClick even. It makes perfect sense. The operating system sends 4 messages for a double-clic sequence. For the left button they are: WM_LBUTTONDOWN WM_LBUTTONUP WM_LBUTTONDBLCLK WM_LBUTTONUP The VCL translates these messages into 5 events: MouseDown MouseUp DoubleClick MouseDown (fired in TControl::WMLButtonDblClk) MouseUp If the cursor has moved appreciably between the first mouse down and the second, or if the MouseDown events are too far apart in time, the DoubleClick doesn't get called. So the first MouseDown is within a couple pixels at most of the location of the double-click. Quote: Every solution will have the same problem. Nope. Some solutions have no problems at all. Quote: Of course GetCursorpos should be called as first statement in the OnDblClick eventhandler. If your program is busy doing something, or something else in the system - which you have no control over - is making the system crawl when the message is sent, your program may not process the double-click message until much later. At that point the mouse cursor could be anywhere on the screen. It doesn't matter at that point whether you call GetCursorPos() immediately or at the last possible moment, you'll still get a nonsense result. Since TControl::WMLButtonDblClk() fires an extra MouseDown event using the position and button data from the Windows WM_LBUTTONDBLCLK message, the only way to get the exact information on where the double-click happened is to set a flag in DblClick and test it in MouseDown. If the flag is set, process a double-click and reset the flag. It's a shame that the VCL doesn't provide positional and button information in the call to OnDblClick, since it's available in the windows message. -- Corey Murtagh The Electric Monk "Quidquid latine dictum sit, altum viditur!" Back to top Corey Murtagh Guest Posted: Wed Apr 28, 2004 9:10 pm    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even Remy Lebeau (TeamB) wrote: Quote: "Corey Murtagh" <emonk (AT) slingshot (DOT) no.uce> wrote in message news:40900f9a (AT) newsgroups (DOT) borland.com... GetCursorPos() will return the /current/ location of the mouse cursor, which may be completely unrelated to its position at the time the double-click event was generated. Possibly, but only if message handling is delayed. If you are not blocking the main VCL thread, then the coordinates will match (to within a few pixels, anyway). Happens all too often unfortunately, especially on machines with limited memory. There's no telling when the OS is going to decide to give a couple of seconds of time to some other process before getting back to you. Quote: Only way to be sure is to save the cursor position at the time of the event... MouseDown or MouseUp. Actually I was wrong. I didn't check before I sent that, although the above method is /almost/ accurate. See my response to Hans for a better explanation and fully accurate solution. Quote: Actually, since OnDblClick is triggered in the context of a WM_LBUTTONDBLCLK message, you could try calling GetMessagePos(), which will return the actual cordinates of the mouse cursor at the time the message was first issued. Of course, if the VCL is simulating that message at any time, GetMessagePos() is useless. It will only work for messages retrieved from the main message queue itself. But it is an alternative to consider. You could intercept WM_LBUTTONDBLCLK, since that message includes positional information anyway. It's possible to be accurate without messing with messages however. -- Corey Murtagh The Electric Monk "Quidquid latine dictum sit, altum viditur!" Back to top Remy Lebeau (TeamB) Guest Posted: Wed Apr 28, 2004 9:57 pm    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even "Corey Murtagh" <emonk (AT) slingshot (DOT) no.uce> wrote Quote: Since TControl::WMLButtonDblClk() fires an extra MouseDown event using the position and button data from the Windows WM_LBUTTONDBLCLK message, the only way to get the exact information on where the double-click happened is to set a flag in DblClick and test it in MouseDown. A better solution is to simply do all of the handling in OnMouseDown only. During a double-click operation, the Shift parameter will include the ssDouble flag. Gambit Back to top Remy Lebeau (TeamB) Guest Posted: Wed Apr 28, 2004 9:58 pm    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even "Corey Murtagh" <emonk (AT) slingshot (DOT) no.uce> wrote Quote: It's a shame that the VCL doesn't provide positional and button information in the call to OnDblClick, since it's available in the windows message. The same could be said for the OnClick event as well. Gambit Back to top Corey Murtagh Guest Posted: Wed Apr 28, 2004 10:17 pm    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even Remy Lebeau (TeamB) wrote: Quote: "Corey Murtagh" <emonk (AT) slingshot (DOT) no.uce> wrote in message news:40901da4 (AT) newsgroups (DOT) borland.com... Since TControl::WMLButtonDblClk() fires an extra MouseDown event using the position and button data from the Windows WM_LBUTTONDBLCLK message, the only way to get the exact information on where the double-click happened is to set a flag in DblClick and test it in MouseDown. A better solution is to simply do all of the handling in OnMouseDown only. During a double-click operation, the Shift parameter will include the ssDouble flag. lol... would you believe I have /never/ seen that flag before? I skipped over it while reading the source and everything. So, our definitive 'position of a double-click' solution: use OnMouseDown and check for shift.Contains(ssDouble). Nice :) -- Corey Murtagh The Electric Monk "Quidquid latine dictum sit, altum viditur!" Back to top Hans Galema Guest Posted: Thu Apr 29, 2004 11:21 am    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even Corey Murtagh wrote: Quote: It makes perfect sense. The operating system sends 4 messages for a double-clic sequence. For the left button they are: WM_LBUTTONDOWN WM_LBUTTONUP WM_LBUTTONDBLCLK WM_LBUTTONUP The VCL translates these messages into 5 events: MouseDown MouseUp DoubleClick MouseDown (fired in TControl::WMLButtonDblClk) MouseUp You omitted one: FormMouseDown FormClick FormMouseUp FormDblClick FormMouseDown FormMouseUp Quote: If the cursor has moved appreciably between the first mouse down and the second, Yes than there is inaccuracy. I always advise a steady hand. <g> Quote: or if the MouseDown events are too far apart in time, the DoubleClick doesn't get called. Indeed. Quote: Nope. Some solutions have no problems at all. Since TControl::WMLButtonDblClk() fires an extra MouseDown event using the position and button data from the Windows WM_LBUTTONDBLCLK message, the only way to get the exact information on where the double-click happened is to set a flag in DblClick and test it in MouseDown. If the flag is set, process a double-click and reset the flag. That could be a nice solution then. The first time I see that here. Quote: It's a shame that the VCL doesn't provide positional and button information in the call to OnDblClick, since it's available in the windows message. Indeed. I was very amazed, when I bought bcb1 and discovered that. That too much object-oriented approch caused many people problems since. Hans. Back to top Hans Galema Guest Posted: Thu Apr 29, 2004 11:25 am    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even Remy Lebeau (TeamB) wrote: Quote: A better solution is to simply do all of the handling in OnMouseDown only. During a double-click operation, the Shift parameter will include the ssDouble flag. Well that is a very nice discovery. How did you find out ? Why didn't you tell before ? Events for a single click: FormMouseDown FormClick FormMouseUp Events for a doubleclick: FormMouseDown FormClick FormMouseUp FormDblClick FormMouseDown Shift Contains ssDouble FormMouseUp I know how you found out. It's in the help for TShiftState. Hans. Back to top Remy Lebeau (TeamB) Guest Posted: Thu Apr 29, 2004 7:43 pm    Post subject: Re: how to detech mouse coordinates X and Y in dblclick even "Hans Galema" <dontusethis (AT) dontusethis (DOT) nl> wrote Quote: Well that is a very nice discovery. How did you find out ? Reading the documentation for starters ;-) TShiftState Type TShiftState indicates the state of the Alt, Ctrl, and Shift keys and the mouse buttons. ... ssDouble The mouse was double-clicked. Then looking at the actual VCL source code to see what it is ACTUALLY doing. 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