Blender source memo

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#blender\source\blender\editors
ED_region_do_draw editors\screen\area.c
	outliner_main_region_draw editors\space_outliner\space_outliner.cc
		draw_outliner editors\space_outliner\outliner_draw.cc
			outliner_buttons
				UI_but_active_only editors\interface\interface.cc
					UI_but_active_only_ex
						ui_but_activate_event editors\interface\interface_handlers.c
							ui_do_button
								ui_do_but_TEX

Python Operator Precedence

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The upper operators have higher precedence than the lower.

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Grouping			()
Function call			f()
Slicing				[index:index]
Array subscription		[]
Bitwise NOT			~x
Unary plus/minus		+, -
Mul/Div/Mod			*, /, %
Add/Sub				+, -
Bitwise shift			<<, >>
Bitwise AND			&
Bitwise XOR			^
Bitwise OR			|
Relation			==, !=, >, >=, <, <=, is, is not, in, not in
				not
				and
				or
				lambda

refer to:
https://discuss.codechef.com/t/operator-precedence-table/14545

Stunning forbidden keyword about QSettings

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    QSettings cfg(CONFIG_INI_PATH, QSettings::IniFormat);
    cfg.beginGroup("general"); // <-- other keywords are all ok.
    std::string val = cfg.value("itemCount").toString().toStdString();
    int video_count = cfg.value("itemCount").toInt();
    cfg.endGroup();

'general' keyword will lead 'val' to output empty in Qt5.15.2.

Notify us socket is ready after WSAEWOULDBLOCK

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Two ways to achieve this goal:

  • Use select api.
  • Use WSAEventSelect and WSAWaitForMultipleEvents. This method is recommended, for we can add a cancellable event along with the socket for polling like GCancellable structure in glib. Cancellable architecture responds smarter than tangible waiting for the ending of sub-modules.

refer to:
gstreamer/subprojects/glib/gio/gsocket.c:g_socket_condition_timed_wait
https://blog.csdn.net/qq_30145355/article/details/78379969

Build FFMpeg in Windows

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In MSYS2 x64 bash,

pacman -S mingw-w64-x86_64-toolchain
pacman -S base-devel
pacman -S yasm nasm gcc

basedir=/d/work/open

cd ${basedir}/x264
./configure --prefix=${basedir}/x264_install --enable-static --extra-cflags="-O0 -g3" --enable-debug
make
make install

cd ${basedir}/ffmpeg
./configure --prefix=${basedir}/ffmpeg_install --enable-static --disable-shared --extra-cflags=-I${basedir}/x264_install/include --extra-ldflags=-L${basedir}/x264_install/lib
make
make install

refer to:
http://events.jianshu.io/p/53ecc4dbe7d0
https://www.videolan.org/developers/x264.html
http://ffmpeg.org/download.html
https://www.msys2.org/
https://git-scm.com/download/win

Perspectively transform points

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After we get the transformation matrix 'trans_mat' from the 'getPerspectiveTransform', we can transform a point in this way

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        cv::Point2f src = cv::Point2f(123, 456);
        std::vector<cv::Point2f> in_pts, out_pts;
        in_pts.push_back(src);
        cv::perspectiveTransform(in_pts, out_pts, trans_mat);
        cv::Point2f dst = out_pts.front();

refer to:
https://blog.csdn.net/xiaowei_cqu/article/details/26478135

MsgWaitForMultipleObjectsEx, indeed core function

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Formerly I wrote message loop code like

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	if (GetMessage (&msg, NULL, 0, 0, PM_REMOVE))
	{
		TranslateMessage (&msg);
		DispatchMessage (&msg);
	}

If no message occured, I couldn't do anything else. It's the reason why I couldn't wrote a cross-platform UI framework which needed to realize IOC abstraction.

In the GStreamer and GLib source code, I learnt from its G_WIN32_MSG_HANDLE processing logic, there is a critical api, MsgWaitForMultipleObjectsEx, which can bundle message and all other types of events together for polling, we needn't repetitively call PeekMessage to query if a message happens, it's ridiculous.

I guess the Qt framework really knows this trick while the Awtk doesn't.

Rtsp memo

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Terms,

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CC: CSRC Counter
CSRC: Contributing Source
SSRC: Synchronization Source
FIR: Full Intra Request, rfc5104
FCI: Feedback Control Information
REMB: Receiver Estimated Max Bitrate
TWCC: Transport wide Congestion Control
RTX: retransmission

Sdp example

v=0
o=- 17618512456233465749 1 IN IP4 127.0.0.1
s=Session streamed with GStreamer
i=rtsp-server
t=0 0
a=tool:GStreamer
a=type:broadcast
a=control:*
a=range:npt=0-
m=video 0 RTP/AVP 96
c=IN IP4 0.0.0.0
b=AS:3000
a=rtpmap:96 H264/90000
a=framerate:30
a=fmtp:96 packetization-mode=1;sprop-parameter-sets=J2QAFKwrYKD9gIgAAAMACAAAAwHnQgAW4gAC3G173wdocKuA,KO48sA==;profile-level-id=640014;level-asymmetry-allowed=1
a=control:stream=0
a=ts-refclk:local
a=mediaclk:sender
a=ssrc:4060724388 cname:user1571168269@host-d3352119

refer to:
https://www.rfc-editor.org/rfc/rfc3550
https://www.rfc-editor.org/rfc/rfc3551
https://www.rfc-editor.org/rfc/rfc2326
https://www.rfc-editor.org/rfc/rfc4588
https://www.rfc-editor.org/rfc/rfc4585
https://www.rfc-editor.org/rfc/rfc7273
https://blog.csdn.net/weixin_42462202/article/details/98986535
https://github.com/fanxiushu/xdisp_virt
https://www.ngui.cc/el/72647.html