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#Basic drawing app free
You might be surprised by how many great free drawing apps for iPad there are. Transversely, free does not mean a bad app. In the land of development, a cost does not mean quality. While there are plenty of high-end drawing apps that come at a cost, there are many free drawing apps for iPad. To share a surface across processes, one thread creates the surface and communicates its surface ID (the sid member of the surface information structure filled in by gf_surface_get_info()).If you have the new iPad Pro, you might be wondering how you can start drawing immediately. When the threads are in different processes, only one thread needs to attach to the display and the layer the shared surface is associated with. Threads, whether in the same or different processes, can render to the same surface.
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It ensures that your thread or process has exclusive access to the hardware in a gf_draw_begin() and gf_draw_end() block, and leaves the hardware in a known state. Be sure to set the GF_SURFACE_CREATE_CPU_FAST_ACCESS flag when you create the source surface using gf_surface_create(). If you are blitting between two surfaces with different formats, and your hardware doesn't support color-space conversion, you should put the source surface in system RAM to improve performance. This selects the surface associated with the context parameter. Note that we pass NULL for the source or destination surface for the scaled blit or gf_draw_blit2(). If you want to scale the area (increasing or decreasing its size), use gf_draw_blitscaled().įor example, to blit the bitmap drawn in the previous example, add these lines of code: Use gf_draw_blit1() to blit within a surface, or gf_draw_blit2() to blit between potentially two surfaces. Gf_draw_bitmap(context, &btmap, 10, 10) Blitting Gf_context_set_fgcolor(context, 0xFFFFFF) Gf_context_set_bgcolor(context, 0xFF0000) If (gf_dev_attach(&gdev, GF_DEVICE_INDEX(0), &gdev_info) != GF_ERR_OK) Associate the surface with the draw context by calling gf_context_set_surface().Ĭalling gf_dev_detach() isn't strictly necessary, as the monitor process io-display will clean up resources when the application exits.Create a draw context by calling gf_context_create().Any call to a gf_layer_set*() function must be followed by gf_layer_update() to make the changes take effect. If you set any of the layer's parameters, commit the changes with gf_layer_update().Set the visible surface for each layer by calling gf_layer_set_surfaces().You can target more than one layer at the same surface. You require at least one surface per layer in order to display an image on that layer. Create a surface for each layer by calling gf_surface_create_layer().You also use this handle to attach a surface to the layer. You need the handle for an attached layer to control any of the layer properties (such as brightness, contrast, and saturation), chroma and alpha blending, and viewports. In the QNX Graphics Framework, displays always have at least one layer (layer 0). Attach to one or more of the display's layers by calling gf_layer_attach().This gives you a display handle, which you require to use hardware cursors and layers for the display. Attach to the device's display (or displays if there's more than one) by calling gf_display_attach().This gives you a handle to the device, which you need to create draw contexts and surfaces, and to attach to displays. Attach to a graphics device by calling gf_dev_attach().Let's look at the steps your application needs to perform to use the GF library for 2D drawing.
#Basic drawing app how to
This chapter shows you how to use the basic functions in the QNX Graphics Framework library. QNX Neutrino Advanced Graphics > Developer's Guide