1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
|
# Overview #
Although focus was and still is on graphical APIs, apitrace has a
generic infrastructure to trace any kind of API:
* the APIs types and calls are specified in Python files in specs
sub-directory;
* there is a type hierarchy in `specs/stdapi.py`, capable of representing
most types in C language, and additional semantic metadata
* Python scripts generate C++ code to trace and serialize calls parameters to
a file, and vice-versa.
* The _Visitor_ design pattern is used to navigate over the types.
* The _Template_ design pattern is used to enable any step of code
generation to be overriden by derived classes, allowing to handle
cases that need special treatment without sacrifycing code reuse.
apitrace's architecture is composed of several layers. Too many to show in a
single graph, so only those relevant for OpenGL API are shown below:
specs
^
|
dispatch <-------------- glws
^ ^
| /
helpers <--- glstate /
^ ^ ^ /
/ \ | /
/ \ | /
trace retrace | /
^ ^ | /
/ \ | /
gltrace glretrace
^ ^ ^ ^
/ | \ \
/ | \ \
/ | \ \
/ | \ \
/ | \ \
glxtrace wgltrace cgltrace qapitrace
Here is a quick synopsis of what the layers do:
* `specs` -- specification of the API, expressed in a Python class hierarchy
* `dispatch` -- runtime dispatch of calls to DLLs (open the DLL, get the symbol
address, and call it passing all arguments as-is)
* `helpers` -- helper functions to determine sizes of arrays, blobs, etc. It
often needs to dispatch calls to give the answers.
* `trace` -- generate C++ code for tracing an API based on its spec
* `gltrace` -- specialization of the tracing generation for GL API, with extra
code to generate
* `glxtrace`,` wgltrace`, `cgltrace` -- specialization of the tracing code for the
GLX, WGL, and CGL APIs.
* `retrace` -- generate C++ code to interpret calls from trace, based on the
API's spec
* `glretrace` -- specialization of the retrace code for the GL API
* `glstate` -- code to dump OpenGL state to a JSON file
* `glws` -- abstraction of the window system specific APIs (GXL, WGL, CGL), to
enable cross-platform portability of `glretrace`
* `qapitrace` -- the GUI; it reads traces directly, and gets JSON state by
invoking `glretrace`
# Coding Style #
These are guidelines for new code. Admittedly some of the existing code hasn't
been updated to follow these conventions yet.
Whitespace (all languages):
* indentation is 4 spaces
* never use tabs as indents, except on Makefiles
* otherwise tab equals to 8 spaces
* separate classes with two empty lines
Naming convention:
* `camelCase` for functions/methods
* `UpperCase` for structures/classes
* `lowercase` for namespaces/modules
* `UPPER_CASE` for #defines
* single underscore prefix for variables/functions in automatically generated
code
C++:
* enclose single statement `if` clauses in `{` `}`, specially for
automatically generated code
* `} else {`
* use `inline` keyword for functions/methods which are called with high-frequency
CMake:
* `lower_case` commands
* space between `(` and precedent name
And when in doubt, be consistent with the existing code.
# Commit policy #
Feature development:
* Existing features in master branch should not degrade at any time, for any
platform. Unless they are seldom used or redundant, and there is agreement.
* In particular, new features / changes must not introduce any sort of
instability when tracing.
While application developers and driver developers may be able to
workaround quirks in apitrace, we want to be able to obtain traces from
non-technical end-users with minimal intervention.
This implies that tracing should not make any non-standard assumptions, and
care must be taken to ensure the tracing code is robust against invalid
parameters, multiple threads, etc.
* It's fine to add new features for only some platforms or APIs.
* Non-trivial changes should be staged in a branch, to allow review and
regression testing. Feature branches should be deleted once they have been
merged.
* Releases are tagged commits from master. There are no stable branches.
Backwards compatibility:
* Backwards binary compatibility with old traces must be always maintained: all
tools, including `glretrace`, must handle old traces without regressions.
* No backwards compatibility guarantees for derived data (ASCII dumps, state,
images, etc).
* There should be no gratuitous changes to command line tool interfaces, but no
guarantees are given.
# Regression testing #
There is a regression test suite under development in
https://github.com/apitrace/apitrace-tests .
# Further reading #
* [Intercepting and Instrumenting COM Applications](https://www.usenix.org/legacy/events/coots99/full_papers/hunt/hunt_html)
* [Proxy-Dll: Intercept Calls to DirectX](http://www.mikoweb.eu/index.php?node=21)
# How to's #
## How to support a new OpenGL extension ##
All OpenGL (and OpenGL ES) function prototypes live in `specs/glapi.py`. This
file is semi-automatically derived from Khronos XML description of OpenGL /
OpenGL ES. To refresh do
$ make -C specs/scripts/ glapi.py
$ meld specs/glapi.py specs/scripts/glapi.py
and then port over new prototypes. See also `specs/scripts/README.markdown`.
The upstream XML description is not rich enough to describe all semantic
details that apitrace needs, therefore one needs to manually tweak the
specifications:
* Fix-up the types of array, blob, and pointer arguments.
* For `glGet*` you can use `"_gl_param_size(pname)"` for automatically determining the number of parameters written, e.g.
GlFunction(Void, "glGetIntegerv", [(GLenum, "pname"), Out(Array(GLint, "_gl_param_size(pname)"), "params")], sideeffects=False),
* Add the `sideeffects=False` keyword argument where appropriate, so that those
calls can be merely ignored by `glretrace`.
* Replace generically type `GLuint` object IDs with typed ones, (e.g., replace
`(GLuint, "texture")` into `(GLtexture, "texture")`, so that `glretrace` can
swizzle the objects IDs, when replaying on a different OpenGL implementation.
|
