有高手指导一下 CMemDC 函数用法

bigbat 2018-01-29 06:17:06

void Learn1View::OnDraw(CDC* pDC)
{
HDC hdcMemDC = NULL;
CGDILearn1Doc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;

// TODO: 在此处为本机数据添加绘制代码
CMemDC dcMem(*pDC, this);
CDC& dc = dcMem.GetDC();

CRect rect;
GetClientRect(rect);

dc.FillSolidRect(rect, GetSysColor(COLOR_WINDOW));

CString strRGB;
strRGB.Format(_T("Fill Color is: %d;"),"2000");

dc.DrawText(strRGB, rect, DT_CENTER);
rect.top += 25;

}
看以上代码，其中的CMemDC 函数得到的是一个内存DC句柄，按道理我没有要求内存句柄dc绘到pDC上的话，是显示不出来的，可是程序运行后是可以显示文字的，有懂的朋友指导一下。

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worldy 2018-01-30

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CMemDC在释构函数里会将内存dcBitBlt到传入的的dc

bigbat 2018-01-30

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谢谢,各位：我也猜到了是在析构时来处理重绘的问题，但是这样设计有些没有底。多亏了是ms的样例代码，才由此一问。

zgl7903 2018-01-30

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CMemDC的设计的绝妙之处在于巧妙的利用的C++函数的构析特性，它的BitBlt是在解析~CMemDC函数中完成的，可以在VS下的afxglobals.cpp下看到其源码，当然这也限制了其使用的作用域范围

走好每一步 2018-01-29

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CMemDC 跟dc用法差不多，不知道你是不是用VS自带的，感觉VS自带的没有外面封的那个好用

schlafenhamster 2018-01-29

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不要 CMemDC(CDC& dc, CWnd* pWnd); 使用 CMemDC(CDC& dc);// 试试

python 3.4 chm api 函数手册

The C programming Language 第二版英文版內容列表 Table of Contents Preface.......................................................... Preface to the first edition..................................... Introduction..................................................... Chapter 1 - A Tutorial Introduction.............................. 1.1 Getting Started................................ 1.2 Variables and Arithmetic Expressions........... 1.3 The for statement.............................. 1.4 Symbolic Constants............................. 1.5 Character Input and Output..................... 1.5.1 File Copying.......................... 1.5.2 Character Counting.................... 1.5.3 Line Counting......................... 1.5.4 Word Counting......................... 1.6 Arrays......................................... 1.7 Functions...................................... 1.8 Arguments - Call by Value...................... 1.9 Character Arrays............................... 1.10 External Variables and Scope.................. Chapter 2 - Types, Operators and Expressions..................... 2.1 Variable Names................................. 2.2 Data Types and Sizes........................... 2.3 Constants...................................... 2.4 Declarations................................... 2.5 Arithmetic Operators........................... 2.6 Relational and Logical Operators............... 2.7 Type Conversions............................... 2.8 Increment and Decrement Operators.............. 2.9 Bitwise Operators.............................. 2.10 Assignment Operators and Expressions.......... 2.11 Conditional Expressions....................... 2.12 Precedence and Order of Evaluation............ Chapter 3 - Control Flow......................................... 3.1 Statements and Blocks.......................... 3.2 If-Else........................................ 3.3 Else-If........................................ 3.4 Switch......................................... 3.5 Loops - While and For.......................... 3.6 Loops - Do-While............................... 3.7 Break and Continue............................. 3.8 Goto and labels................................ Chapter 4 - Functions and Program Structure...................... 4.1 Basics of Functions............................ 4.2 Functions Returning Non-integers............... 4.3 External Variables............................. 4.4 Scope Rules.................................... 4.5 Header Files................................... 4.6 Static Variables................................ 4.7 Register Variables.............................. 4.8 Block Structure................................. 4.9 Initialization.................................. 4.10 Recursion...................................... 4.11 The C Preprocessor............................. 4.11.1 File Inclusion........................ 4.11.2 Macro Substitution.................... 4.11.3 Conditional Inclusion................. Chapter 5 - Pointers and Arrays.................................. 5.1 Pointers and Addresses......................... 5.2 Pointers and Function Arguments................ 5.3 Pointers and Arrays............................ 5.4 Address Arithmetic............................. 5.5 Character Pointers and Functions............... 5.6 Pointer Arrays; Pointers to Pointers........... 5.7 Multi-dimensional Arrays....................... 5.8 Initialization of Pointer Arrays............... 5.9 Pointers vs. Multi-dimensional Arrays.......... 5.10 Command-line Arguments........................ 5.11 Pointers to Functions......................... 5.12 Complicated Declarations...................... Chapter 6 - Structures........................................... 6.1 Basics of Structures........................... 6.2 Structures and Functions....................... 6.3 Arrays of Structures........................... 6.4 Pointers to Structures......................... 6.5 Self-referential Structures.................... 6.6 Table Lookup................................... 6.7 Typedef........................................ 6.8 Unions......................................... 6.9 Bit-fields..................................... Chapter 7 - Input and Output..................................... 7.1 Standard Input and Output....................... 7.2 Formatted Output - printf....................... 7.3 Variable-length Argument Lists.................. 7.4 Formatted Input - Scanf......................... 7.5 File Access..................................... 7.6 Error Handling - Stderr and Exit................ 7.7 Line Input and Output........................... 7.8 Miscellaneous Functions......................... 7.8.1 String Operations...................... 7.8.2 Character Class Testing and Conversion. 7.8.3 Ungetc................................. 7.8.4 Command Execution...................... 7.8.5 Storage Management..................... 7.8.6 Mathematical Functions................. 7.8.7 Random Number generation............... Chapter 8 - The UNIX System Interface............................ 8.1 File Descriptors............................... 8.2 Low Level I/O - Read and Write................. 8.3 Open, Creat, Close, Unlink..................... 8.4 Random Access - Lseek.......................... 8.5 Example - An implementation of Fopen and Getc.. 8.6 Example - Listing Directories.................. 8.7 Example - A Storage Allocator.................. Appendix A - Reference Manual.................................... A.1 Introduction................................... A.2 Lexical Conventions............................ A.2.1 Tokens................................ A.2.2 Comments.............................. A.2.3 Identifiers........................... A.2.4 Keywords.............................. A.2.5 Constants............................. A.2.6 String Literals....................... A.3 Syntax Notation................................ A.4 Meaning of Identifiers......................... A.4.1 Storage Class......................... A.4.2 Basic Types........................... A.4.3 Derived types......................... A.4.4 Type Qualifiers....................... A.5 Objects and Lvalues............................ A.6 Conversions.................................... A.6.1 Integral Promotion.................... A.6.2 Integral Conversions.................. A.6.3 Integer and Floating.................. A.6.4 Floating Types........................ A.6.5 Arithmetic Conversions................ A.6.6 Pointers and Integers................. A.6.7 Void.................................. A.6.8 Pointers to Void...................... A.7 Expressions.................................... A.7.1 Pointer Conversion.................... A.7.2 Primary Expressions................... A.7.3 Postfix Expressions................... A.7.4 Unary Operators....................... A.7.5 Casts................................. A.7.6 Multiplicative Operators.............. A.7.7 Additive Operators.................... A.7.8 Shift Operators....................... A.7.9 Relational Operators.................. A.7.10 Equality Operators................... A.7.11 Bitwise AND Operator................. A.7.12 Bitwise Exclusive OR Operator........ A.7.13 Bitwise Inclusive OR Operator........ A.7.14 Logical AND Operator................. A.7.15 Logical OR Operator.................. A.7.16 Conditional Operator................. A.7.17 Assignment Expressions............... A.7.18 Comma Operator.......................... A.7.19 Constant Expressions.................... A.8 Declarations..................................... A.8.1 Storage Class Specifiers................. A.8.2 Type Specifiers.......................... A.8.3 Structure and Union Declarations......... A.8.4 Enumerations............................. A.8.5 Declarators.............................. A.8.6 Meaning of Declarators................... A.8.7 Initialization........................... A.8.8 Type names............................... A.8.9 Typedef.................................. A.8.10 Type Equivalence........................ A.9 Statements....................................... A.9.1 Labeled Statements....................... A.9.2 Expression Statement..................... A.9.3 Compound Statement....................... A.9.4 Selection Statements..................... A.9.5 Iteration Statements..................... A.9.6 Jump statements.......................... A.10 External Declarations........................... A.10.1 Function Definitions.................... A.10.2 External Declarations................... A.11 Scope and Linkage............................... A.11.1 Lexical Scope........................... A.11.2 Linkage................................. A.12 Preprocessing................................... A.12.1 Trigraph Sequences...................... A.12.2 Line Splicing........................... A.12.3 Macro Definition and Expansion.......... A.12.4 File Inclusion.......................... A.12.5 Conditional Compilation................. A.12.6 Line Control............................ A.12.7 Error Generation........................ A.12.8 Pragmas................................. A.12.9 Null directive.......................... A.12.10 Predefined names....................... A.13 Grammar......................................... Appendix B - Standard Library.................................... B.1.1 File Operations................................ B.1.2 Formatted Output......................... B.1.3 Formatted Input.......................... B.1.4 Character Input and Output Functions..... B.1.5 Direct Input and Output Functions........ B.1.6 File Positioning Functions............... B.1.7 Error Functions.......................... B.2 Character Class Tests: ................. B.3 String Functions: ..................... B.4 Mathematical Functions: ................. B.5 Utility Functions: ....................

c++ primer第五版第6章答案

LinuxUNIX系统编程手册非常适合新手学习的好资料

详细介绍了STM32f系列32位控制器的固件库，对每一个函数都进行了详细的说明，内容详实，适合初学者参考使用

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