Drawing and Displaying Simple Text (C/C++)

Overview

In a simple user interface, only a few lines of static text need to be displayed, such as the text on a label, button, menu item, or status bar. In this case, you only need to select a proper font, size, and color to complete the rendering.

Available APIs

API Definition	Description
OH_Drawing_TextStyle* OH_Drawing_CreateTextStyle(void)	Creates an OH_Drawing_TextStyle object.
void OH_Drawing_SetTextStyleFontSize(OH_Drawing_TextStyle* style, double fontSize)	Sets the font size for a text style.
void OH_Drawing_SetTextStyleFontWeight(OH_Drawing_TextStyle* style, int fontWeight)	Sets the font weight for a text style. Currently, only the default system font supports font weight adjustment. For other fonts, if the weight is less than semi-bold, there is no variation in stroke thickness. If the weight is greater than or equal to semi-bold, it might result in a fake bold effect.

How to Develop

1. Create a canvas object. For details about how to create a canvas object, see Obtaining a Canvas and Displaying Drawing Results (C/C++).

2. Initialize the paragraph style and set the text alignment to center alignment.

   // Create a TypographyStyle object, which is required for creating Typography.
   OH_Drawing_TypographyStyle *typoStyle = OH_Drawing_CreateTypographyStyle();
   // Set the text alignment mode to center.
   OH_Drawing_SetTypographyTextAlign(typoStyle, TEXT_ALIGN_CENTER);
   

   sample_bitmap.cpp

3. Initialize the text style. Here, the font color is set to pure black, the font size to 60, and the font weight to 400.

   // Set the text color, size, and weight. If TextStyle is not set, the default TextStyle in TypographyStyle is used.
   OH_Drawing_TextStyle *txtStyle = OH_Drawing_CreateTextStyle();
   OH_Drawing_SetTextStyleColor(txtStyle, OH_Drawing_ColorSetArgb(0xFF, 0x00, 0x00, 0x00));
   OH_Drawing_SetTextStyleFontSize(txtStyle, 60);
   OH_Drawing_SetTextStyleFontWeight(txtStyle, FONT_WEIGHT_400);
   

   sample_bitmap.cpp

4. Initialize the paragraph object and add text.

   // Create a FontCollection object to manage the font matching logic.
   OH_Drawing_FontCollection *fc = OH_Drawing_CreateFontCollection();
   // Use the FontCollection object and the created TypographyStyle object to create a TypographyCreate object, which is used to create a Typography object.
   OH_Drawing_TypographyCreate *handler = OH_Drawing_CreateTypographyHandler(typoStyle, fc);
   
   // Add the created TextStyle object to handler.
   OH_Drawing_TypographyHandlerPushTextStyle(handler, txtStyle);
   // Add text to handler.
   const char *text = "Hello World Drawing\n";
   OH_Drawing_TypographyHandlerAddText(handler, text);
   
   OH_Drawing_Typography *typography = OH_Drawing_CreateTypography(handler);
   

   sample_bitmap.cpp

5. Layout the paragraph and draw the text.

   // Set the maximum width.
   double maxWidth = width_;
   OH_Drawing_TypographyLayout(typography, maxWidth);
   // Draw the text on the canvas.
   OH_Drawing_TypographyPaint(typography, cCanvas_, 0, 100);
   

   sample_bitmap.cpp

6. Release the memory.

   // Release the memory.
   OH_Drawing_DestroyTypographyStyle(typoStyle);
   OH_Drawing_DestroyTextStyle(txtStyle);
   OH_Drawing_DestroyFontCollection(fc);
   OH_Drawing_DestroyTypographyHandler(handler);
   OH_Drawing_DestroyTypography(typography);
   

   sample_bitmap.cpp

Effect