From d19b5db5dce92efd55359607006a32076dc95d12 Mon Sep 17 00:00:00 2001 From: Brian Paul Date: Wed, 23 Jul 2003 15:45:25 +0000 Subject: fill in chapter 5, 6 text --- docs/MESA_program_debug.spec | 173 ++++++++++++++++++++++++++++++------------- 1 file changed, 122 insertions(+), 51 deletions(-) (limited to 'docs') diff --git a/docs/MESA_program_debug.spec b/docs/MESA_program_debug.spec index 67115532c2..e9eaa82d89 100644 --- a/docs/MESA_program_debug.spec +++ b/docs/MESA_program_debug.spec @@ -8,7 +8,7 @@ Name Strings Contact - Brian Paul (brian_e_paul 'at' yahoo.com) + Brian Paul (brian @ tungstengraphics.com) Status @@ -18,7 +18,7 @@ Version Last Modified Date: July 20, 2003 Author Revision: 1.0 - $Date: 2003/07/21 04:23:32 $ $Revision: 1.1 $ + $Date: 2003/07/23 15:45:25 $ $Revision: 1.2 $ Number @@ -41,21 +41,19 @@ Overview only provides the minimal hooks required to implement a debugger. There are facilities to do the following: - 1. Query the current values of input, output and temporary registers. - 2. Query the current program position during execution. - 3. Have the GL call a user-specified function prior to executing + 1. Have the GL call a user-specified function prior to executing each vertex or fragment instruction. + 2. Query the current program string's execution position. + 3. Query the current values of intermediate program values. The main feature is the ProgramCallbackMESA function. It allows the user to register a callback function with the GL. The callback will be called prior to executing each vertex or fragment program instruction. - The callback function can determine whether to return immediately (to - continue program execution) or stop and process user commands. From within the callback, the user may issue glGet* commands to query current GL state. The GetProgramRegisterfvMESA function allows - all program register values to be queried (such as temporaries, - input attributes, and result registers). + current program values to be queried (such as temporaries, input + attributes, and result registers). There are flags for enabling/disabling the program callbacks. @@ -88,7 +86,8 @@ Issues programs I don't see another way to do it. 3. How do we prevent the user from doing something crazy in the - callback function, like trying to call glBegin? + callback function, like trying to call glBegin (leading to + recursion)? The rule is that the callback function can only issue glGet*() functions and no other GL commands. It could be difficult to @@ -98,8 +97,19 @@ Issues 4. Is this extension amenable to hardware implementation? - Unresolved, but we'd hope so. Perhaps the GL implementation - will have to fall back to a software path when debugging. + Hopefully, but if not, the GL implementation will have to fall + back to a software path when debugging. This may be acceptable + for debugging. + + 5. What's the parameter to ProgramCallbackMESA for? + + It's a common programming practice to associate a user-supplied + value with callback functions. + + 6. Debuggers often allow one to modify intermediate program values, + then continue. Does this extension support that? + + No. New Procedures and Functions (and datatypes) @@ -148,17 +158,73 @@ Operations and the Frame Buffer) Additions to Chapter 5 of the OpenGL 1.4 Specification (Special Functions) - XXX Document ProgramCallbackMESA here + In section 5.4 "Display Lists", page 202, add the following command + to the list of those that are not compiled into display lists: + ProgramCallbackMESA. + + + Add a new section 5.7 "Callback Functions" + + The function + + void ProgramCallbackMESA(enum target, programcallbackMESA callback, + void *data) + + registers a user-defined callback function with the GL. may + be FRAGMENT_PROGRAM_ARB or VERTEX_PROGRAM_ARB. Callbacks registered + with these targets will be called prior to executing each instruction + in the current fragment or vertex program, respectively. The callbacks + are enabled and disabled by calling Enable or Disable with + FRAGMENT_PROGRAM_ARB or VERTEX_PROGRAM_ARB. - Add to the list of functions which cannot be included in display - lists: ProgramCallbackMESA. + The callback function's signature must match the typedef + + typedef void (*programcallbackMESA)(enum target, void *data) + + When the callback function is called, will either be + FRAGMENT_PROGRAM_ARB or VERTEX_PROGRAM_ARB to indicate which + program is currently executing and will be the value + specified when ProgramCallbackMESA was called. + + From within the callback function, only the following GL commands + may be called: + + GetBooleanv + GetDoublev + GetFloatv + GetIntegerv + GetProgramLocalParameter + GetProgramEnvParameter + GetProgramRegisterfvMESA + GetProgramivARB + GetProgramStringARB + GetError + + Calling any other command from within the callback results in + undefined behaviour. Additions to Chapter 6 of the OpenGL 1.4 Specification (State and State Requests) - XXX document GetProgramRegisterfvMESA here + Add a new section 6.1.3 "Program Value Queries": + The command + + void GetProgramRegisterfvMESA(enum target, sizei len, + const ubyte *registerName, + float *v) + + Is used to query the value of program variables and registers + during program execution. GetProgramRegisterMESA may only be + called from within a callback function registered with + ProgramCallbackMESA. + + and specify the string name of a program + register (such as "R3"), input attribute (such as "vertex.color"), + an output attribute (such as "result.texcoord[0]") or a user- + defined identifier. The current value of that variable is + returned as four floats in . Additions to Appendix A of the OpenGL 1.4 Specification (Invariance) @@ -191,9 +257,7 @@ Errors Note: INVALID_OPERAION IS NOT generated by GetProgramRegisterfvMESA, GetBooleanv, GetDoublev, GetFloatv, or GetIntegerv if called between - Begin and End. - These functions may be called from the user-provided callback function - which is called between Begin/End. + Begin and End when a vertex or fragment program is currently executing. INVALID_ENUM is generated by ProgramCallbackMESA, GetProgramRegisterfvMESA if is not a program target supported @@ -201,7 +265,7 @@ Errors NV_fragment_program). INVALID_VALUE is generated by GetProgramRegisterfvMESA if - is not a recognized program register. + does not name a known program register or variable. INVALID_OPERATION is generated by GetProgramRegisterfvMESA when a register query is attempted for a program target that's not currently @@ -239,47 +303,54 @@ Revision History Second draft. (Brian Paul) 20 July 2003 Third draft. Lots of fundamental changes. (Brian Paul) + 23 July 2003 + Added chapter 5 and 6 spec language. (Brian Paul) Example Usage -/* This is called by the GL when the vertex program is executing. - * We can only make glGet* calls from within this function! - */ -void DebugCallback(GLenum target, GLvoid *data) -{ - GLint pos; - GLuint i; + The following is a very simple example of how this extension may + be used to print the values of R0, R1, R2 and R3 while executing + vertex programs. + + + /* This is called by the GL when the vertex program is executing. + * We can only make glGet* calls from within this function! + */ + void DebugCallback(GLenum target, GLvoid *data) + { + GLint pos; + GLuint i; - /* Get PC and current instruction string */ - glGetIntegerv(GL_VERTEX_PROGRAM_POSITION_ARB, &pos); + /* Get PC and current instruction string */ + glGetIntegerv(GL_VERTEX_PROGRAM_POSITION_ARB, &pos); - printf("Current position: %d\n", pos); + printf("Current position: %d\n", pos); - printf("Current temporary registers:\n"); - for (i = 0; i < 4; i++) { - GLfloat v[4]; - char s[10]; - sprintf(s, "R%d", i); - glGetProgramRegisterfvMESA(GL_VERTEX_PROGRAM_ARB, strlen(s), s, v); - printf("R%d = %g, %g, %g, %g\n", i, v[0], v[1], v[2], v[3]); - } -} + printf("Current temporary registers:\n"); + for (i = 0; i < 4; i++) { + GLfloat v[4]; + char s[10]; + sprintf(s, "R%d", i); + glGetProgramRegisterfvMESA(GL_VERTEX_PROGRAM_ARB, strlen(s), s, v); + printf("R%d = %g, %g, %g, %g\n", i, v[0], v[1], v[2], v[3]); + } + } - /* - * elsewhere... - */ + /* + * elsewhere... + */ - /* Register our debugger callback function */ - glProgramCallbackMESA(GL_VERTEX_PROGRAM_ARB, DebugCallback, NULL); - glEnable(GL_VERTEX_PROGRAM_CALLBACK_MESA); + /* Register our debugger callback function */ + glProgramCallbackMESA(GL_VERTEX_PROGRAM_ARB, DebugCallback, NULL); + glEnable(GL_VERTEX_PROGRAM_CALLBACK_MESA); - /* define/bind a vertex program */ + /* define/bind a vertex program */ - glEnable(GL_VERTEX_PROGRAM); + glEnable(GL_VERTEX_PROGRAM); - /* render something */ - glBegin(GL_POINTS); - glVertex2f(0, 0); - glEnd(); + /* render something */ + glBegin(GL_POINTS); + glVertex2f(0, 0); + glEnd(); -- cgit v1.2.3