Rework OpenGL renderer.

The OpenGL renderer has been revised, with the following changes:
 - Initialization and rendering have been refactored to reduce the number of
   redundant objects used.
 - Framebuffer rotation is now done directly, using texture mapping.
 - Vertex coordinates are now given in pixels, and the projection matrix
   isn't hardcoded anymore.
This commit is contained in:
Yuri Kunde Schlesner 2014-08-28 15:21:54 -03:00 committed by Tony Wasserka
parent fec7f6b035
commit 11642fd3a2
4 changed files with 185 additions and 225 deletions

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@ -6,34 +6,40 @@
namespace GLShaders {
static const char g_vertex_shader[] = R"(
const char g_vertex_shader[] = R"(
#version 150 core
in vec3 position;
in vec2 texCoord;
out vec2 UV;
in vec2 vert_position;
in vec2 vert_tex_coord;
out vec2 frag_tex_coord;
mat3 window_scale = mat3(
vec3(1.0, 0.0, 0.0),
vec3(0.0, 5.0/6.0, 0.0), // TODO(princesspeachum): replace hard-coded aspect with uniform
vec3(0.0, 0.0, 1.0)
);
// This is a truncated 3x3 matrix for 2D transformations:
// The upper-left 2x2 submatrix performs scaling/rotation/mirroring.
// The third column performs translation.
// The third row could be used for projection, which we don't need in 2D. It hence is assumed to
// implicitly be [0, 0, 1]
uniform mat3x2 modelview_matrix;
void main() {
gl_Position.xyz = window_scale * position;
gl_Position.w = 1.0;
// Multiply input position by the rotscale part of the matrix and then manually translate by
// the last column. This is equivalent to using a full 3x3 matrix and expanding the vector
// to `vec3(vert_position.xy, 1.0)`
gl_Position = vec4(mat2(modelview_matrix) * vert_position + modelview_matrix[2], 0.0, 1.0);
frag_tex_coord = vert_tex_coord;
}
)";
UV = texCoord;
})";
static const char g_fragment_shader[] = R"(
const char g_fragment_shader[] = R"(
#version 150 core
in vec2 UV;
out vec3 color;
uniform sampler2D sampler;
in vec2 frag_tex_coord;
out vec4 color;
uniform sampler2D color_texture;
void main() {
color = texture(sampler, UV).rgb;
})";
color = texture(color_texture, frag_tex_coord);
}
)";
}

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@ -3,64 +3,51 @@
// Refer to the license.txt file included.
#include "core/hw/gpu.h"
#include "core/mem_map.h"
#include "common/emu_window.h"
#include "video_core/video_core.h"
#include "video_core/renderer_opengl/renderer_opengl.h"
#include "video_core/renderer_opengl/gl_shader_util.h"
#include "video_core/renderer_opengl/gl_shaders.h"
#include "core/mem_map.h"
#include <algorithm>
static const GLfloat kViewportAspectRatio =
(static_cast<float>(VideoCore::kScreenTopHeight) + VideoCore::kScreenBottomHeight) / VideoCore::kScreenTopWidth;
/**
* Vertex structure that the drawn screen rectangles are composed of.
*/
struct ScreenRectVertex {
ScreenRectVertex(GLfloat x, GLfloat y, GLfloat u, GLfloat v) {
position[0] = x;
position[1] = y;
tex_coord[0] = u;
tex_coord[1] = v;
}
// Fullscreen quad dimensions
static const GLfloat kTopScreenWidthNormalized = 2;
static const GLfloat kTopScreenHeightNormalized = kTopScreenWidthNormalized * (static_cast<float>(VideoCore::kScreenTopHeight) / VideoCore::kScreenTopWidth);
static const GLfloat kBottomScreenWidthNormalized = kTopScreenWidthNormalized * (static_cast<float>(VideoCore::kScreenBottomWidth) / VideoCore::kScreenTopWidth);
static const GLfloat kBottomScreenHeightNormalized = kBottomScreenWidthNormalized * (static_cast<float>(VideoCore::kScreenBottomHeight) / VideoCore::kScreenBottomWidth);
static const GLfloat g_vbuffer_top[] = {
// x, y z u v
-1.0f, 0.0f, 0.0f, 0.0f, 1.0f,
1.0f, 0.0f, 0.0f, 1.0f, 1.0f,
1.0f, kTopScreenHeightNormalized, 0.0f, 1.0f, 0.0f,
1.0f, kTopScreenHeightNormalized, 0.0f, 1.0f, 0.0f,
-1.0f, kTopScreenHeightNormalized, 0.0f, 0.0f, 0.0f,
-1.0f, 0.0f, 0.0f, 0.0f, 1.0f
GLfloat position[2];
GLfloat tex_coord[2];
};
static const GLfloat g_vbuffer_bottom[] = {
// x y z u v
-(kBottomScreenWidthNormalized / 2), -kBottomScreenHeightNormalized, 0.0f, 0.0f, 1.0f,
(kBottomScreenWidthNormalized / 2), -kBottomScreenHeightNormalized, 0.0f, 1.0f, 1.0f,
(kBottomScreenWidthNormalized / 2), 0.0f, 0.0f, 1.0f, 0.0f,
(kBottomScreenWidthNormalized / 2), 0.0f, 0.0f, 1.0f, 0.0f,
-(kBottomScreenWidthNormalized / 2), 0.0f, 0.0f, 0.0f, 0.0f,
-(kBottomScreenWidthNormalized / 2), -kBottomScreenHeightNormalized, 0.0f, 0.0f, 1.0f
};
/**
* Defines a 1:1 pixel ortographic projection matrix with (0,0) on the top-left
* corner and (width, height) on the lower-bottom.
*
* The projection part of the matrix is trivial, hence these operations are represented
* by a 3x2 matrix.
*/
static std::array<GLfloat, 3*2> MakeOrthographicMatrix(const float width, const float height) {
std::array<GLfloat, 3*2> matrix;
matrix[0] = 2.f / width; matrix[2] = 0.f; matrix[4] = -1.f;
matrix[1] = 0.f; matrix[3] = -2.f / height; matrix[5] = 1.f;
// Last matrix row is implicitly assumed to be [0, 0, 1].
return matrix;
}
/// RendererOpenGL constructor
RendererOpenGL::RendererOpenGL() {
resolution_width = std::max(VideoCore::kScreenTopWidth, VideoCore::kScreenBottomWidth);
resolution_height = VideoCore::kScreenTopHeight + VideoCore::kScreenBottomHeight;
// Initialize screen info
const auto& framebuffer_top = GPU::g_regs.framebuffer_config[0];
const auto& framebuffer_sub = GPU::g_regs.framebuffer_config[1];
screen_info.Top().width = VideoCore::kScreenTopWidth;
screen_info.Top().height = VideoCore::kScreenTopHeight;
screen_info.Top().stride = framebuffer_top.stride;
screen_info.Top().flipped_xfb_data = xfb_top_flipped;
screen_info.Bottom().width = VideoCore::kScreenBottomWidth;
screen_info.Bottom().height = VideoCore::kScreenBottomHeight;
screen_info.Bottom().stride = framebuffer_sub.stride;
screen_info.Bottom().flipped_xfb_data = xfb_bottom_flipped;
}
/// RendererOpenGL destructor
@ -71,16 +58,23 @@ RendererOpenGL::~RendererOpenGL() {
void RendererOpenGL::SwapBuffers() {
render_window->MakeCurrent();
// EFB->XFB copy
// TODO(bunnei): This is a hack and does not belong here. The copy should be triggered by some
// register write.
//
// TODO(princesspeachum): (related to above^) this should only be called when there's new data, not every frame.
// Currently this uploads data that shouldn't have changed.
Common::Rect framebuffer_size(0, 0, resolution_width, resolution_height);
RenderXFB(framebuffer_size, framebuffer_size);
for(int i : {0, 1}) {
const auto& framebuffer = GPU::g_regs.framebuffer_config[i];
if (textures[i].width != framebuffer.width || textures[i].height != framebuffer.height) {
// Reallocate texture if the framebuffer size has changed.
// This is expected to not happen very often and hence should not be a
// performance problem.
glBindTexture(GL_TEXTURE_2D, textures[i].handle);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, framebuffer.width, framebuffer.height, 0,
GL_BGR, GL_UNSIGNED_BYTE, nullptr);
textures[i].width = framebuffer.width;
textures[i].height = framebuffer.height;
}
LoadFBToActiveGLTexture(GPU::g_regs.framebuffer_config[i], textures[i]);
}
// XFB->Window copy
DrawScreens();
// Swap buffers
@ -89,115 +83,110 @@ void RendererOpenGL::SwapBuffers() {
}
/**
* Helper function to flip framebuffer from left-to-right to top-to-bottom
* @param raw_data Pointer to input raw framebuffer in V/RAM
* @param screen_info ScreenInfo structure with screen size and output buffer pointer
* @todo Early on hack... I'd like to find a more efficient way of doing this /bunnei
* Loads framebuffer from emulated memory into the active OpenGL texture.
*/
void RendererOpenGL::FlipFramebuffer(const u8* raw_data, ScreenInfo& screen_info) {
for (int x = 0; x < screen_info.width; x++) {
int in_coord = x * screen_info.stride;
for (int y = screen_info.height-1; y >= 0; y--) {
// TODO: Properly support other framebuffer formats
int out_coord = (x + y * screen_info.width) * 3;
screen_info.flipped_xfb_data[out_coord] = raw_data[in_coord + 2]; // Red
screen_info.flipped_xfb_data[out_coord + 1] = raw_data[in_coord + 1]; // Green
screen_info.flipped_xfb_data[out_coord + 2] = raw_data[in_coord]; // Blue
in_coord += 3;
}
}
}
void RendererOpenGL::LoadFBToActiveGLTexture(const GPU::Regs::FramebufferConfig& framebuffer,
const TextureInfo& texture) {
const VAddr framebuffer_vaddr = Memory::PhysicalToVirtualAddress(
framebuffer.active_fb == 1 ? framebuffer.address_left2 : framebuffer.address_left1);
/**
* Renders external framebuffer (XFB)
* @param src_rect Source rectangle in XFB to copy
* @param dst_rect Destination rectangle in output framebuffer to copy to
*/
void RendererOpenGL::RenderXFB(const Common::Rect& src_rect, const Common::Rect& dst_rect) {
const auto& framebuffer_top = GPU::g_regs.framebuffer_config[0];
const auto& framebuffer_sub = GPU::g_regs.framebuffer_config[1];
const u32 active_fb_top = (framebuffer_top.active_fb == 1)
? Memory::PhysicalToVirtualAddress(framebuffer_top.address_left2)
: Memory::PhysicalToVirtualAddress(framebuffer_top.address_left1);
const u32 active_fb_sub = (framebuffer_sub.active_fb == 1)
? Memory::PhysicalToVirtualAddress(framebuffer_sub.address_left2)
: Memory::PhysicalToVirtualAddress(framebuffer_sub.address_left1);
DEBUG_LOG(GPU, "0x%08x bytes from 0x%08x(%dx%d), fmt %x",
framebuffer.stride * framebuffer.height,
framebuffer_vaddr, (int)framebuffer.width,
(int)framebuffer.height, (int)framebuffer.format);
DEBUG_LOG(GPU, "RenderXFB: 0x%08x bytes from 0x%08x(%dx%d), fmt %x",
framebuffer_top.stride * framebuffer_top.height,
active_fb_top, (int)framebuffer_top.width,
(int)framebuffer_top.height, (int)framebuffer_top.format);
const u8* framebuffer_data = Memory::GetPointer(framebuffer_vaddr);
FlipFramebuffer(Memory::GetPointer(active_fb_top), screen_info.Top());
FlipFramebuffer(Memory::GetPointer(active_fb_sub), screen_info.Bottom());
// TODO: Handle other pixel formats
_dbg_assert_msg_(RENDER, framebuffer.color_format == GPU::Regs::PixelFormat::RGB8,
"Unsupported 3DS pixel format.");
for (int i = 0; i < 2; i++) {
ScreenInfo* current_screen = &screen_info[i];
size_t pixel_stride = framebuffer.stride / 3;
// OpenGL only supports specifying a stride in units of pixels, not bytes, unfortunately
_dbg_assert_(RENDER, pixel_stride * 3 == framebuffer.stride);
// Ensure no bad interactions with GL_UNPACK_ALIGNMENT, which by default
// only allows rows to have a memory alignement of 4.
_dbg_assert_(RENDER, pixel_stride % 4 == 0);
glBindTexture(GL_TEXTURE_2D, current_screen->texture_id);
glBindTexture(GL_TEXTURE_2D, texture.handle);
glPixelStorei(GL_UNPACK_ROW_LENGTH, (GLint)pixel_stride);
// TODO: This should consider the GPU registers for framebuffer width, height and stride.
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, current_screen->width, current_screen->height,
GL_RGB, GL_UNSIGNED_BYTE, current_screen->flipped_xfb_data);
}
// Update existing texture
// TODO: Test what happens on hardware when you change the framebuffer dimensions so that they
// differ from the LCD resolution.
// TODO: Applications could theoretically crash Citra here by specifying too large
// framebuffer sizes. We should make sure that this cannot happen.
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, framebuffer.width, framebuffer.height,
GL_BGR, GL_UNSIGNED_BYTE, framebuffer_data);
glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
glBindTexture(GL_TEXTURE_2D, 0);
// TODO(princesspeachum):
// Only the subset src_rect of the GPU buffer
// should be copied into the texture of the relevant screen.
//
// The method's parameters also only include src_rect and dest_rec for one screen,
// so this may need to be changed (pair for each screen).
}
/**
* Initializes the OpenGL state and creates persistent objects.
*/
void RendererOpenGL::InitOpenGLObjects() {
glGenVertexArrays(1, &vertex_array_id);
glBindVertexArray(vertex_array_id);
glClearColor(1.0f, 1.0f, 1.0f, 0.0f);
glDisable(GL_DEPTH_TEST);
// Link shaders and get variable locations
program_id = ShaderUtil::LoadShaders(GLShaders::g_vertex_shader, GLShaders::g_fragment_shader);
sampler_id = glGetUniformLocation(program_id, "sampler");
attrib_position = glGetAttribLocation(program_id, "position");
attrib_texcoord = glGetAttribLocation(program_id, "texCoord");
uniform_modelview_matrix = glGetUniformLocation(program_id, "modelview_matrix");
uniform_color_texture = glGetUniformLocation(program_id, "color_texture");
attrib_position = glGetAttribLocation(program_id, "vert_position");
attrib_tex_coord = glGetAttribLocation(program_id, "vert_tex_coord");
// Generate vertex buffers for both screens
glGenBuffers(1, &screen_info.Top().vertex_buffer_id);
glGenBuffers(1, &screen_info.Bottom().vertex_buffer_id);
// Generate VBO handle for drawing
glGenBuffers(1, &vertex_buffer_handle);
// Attach vertex data for top screen
glBindBuffer(GL_ARRAY_BUFFER, screen_info.Top().vertex_buffer_id);
glBufferData(GL_ARRAY_BUFFER, sizeof(g_vbuffer_top), g_vbuffer_top, GL_STATIC_DRAW);
// Generate VAO
glGenVertexArrays(1, &vertex_array_handle);
glBindVertexArray(vertex_array_handle);
// Attach vertex data for bottom screen
glBindBuffer(GL_ARRAY_BUFFER, screen_info.Bottom().vertex_buffer_id);
glBufferData(GL_ARRAY_BUFFER, sizeof(g_vbuffer_bottom), g_vbuffer_bottom, GL_STATIC_DRAW);
// Attach vertex data to VAO
glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_handle);
glBufferData(GL_ARRAY_BUFFER, sizeof(ScreenRectVertex) * 4, nullptr, GL_STREAM_DRAW);
glVertexAttribPointer(attrib_position, 2, GL_FLOAT, GL_FALSE, sizeof(ScreenRectVertex), (GLvoid*)offsetof(ScreenRectVertex, position));
glVertexAttribPointer(attrib_tex_coord, 2, GL_FLOAT, GL_FALSE, sizeof(ScreenRectVertex), (GLvoid*)offsetof(ScreenRectVertex, tex_coord));
glEnableVertexAttribArray(attrib_position);
glEnableVertexAttribArray(attrib_tex_coord);
// Create color buffers for both screens
glGenTextures(1, &screen_info.Top().texture_id);
glGenTextures(1, &screen_info.Bottom().texture_id);
// Allocate textures for each screen
for (auto& texture : textures) {
glGenTextures(1, &texture.handle);
for (int i = 0; i < 2; i++) {
ScreenInfo* current_screen = &screen_info[i];
// Allocate texture
glBindTexture(GL_TEXTURE_2D, current_screen->vertex_buffer_id);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, current_screen->width, current_screen->height,
0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
// Allocation of storage is deferred until the first frame, when we
// know the framebuffer size.
glBindTexture(GL_TEXTURE_2D, texture.handle);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
}
glBindTexture(GL_TEXTURE_2D, 0);
}
/**
* Draws a single texture to the emulator window, rotating the texture to correct for the 3DS's LCD rotation.
*/
void RendererOpenGL::DrawSingleScreenRotated(const TextureInfo& texture, float x, float y, float w, float h) {
std::array<ScreenRectVertex, 4> vertices = {
ScreenRectVertex(x, y, 1.f, 0.f),
ScreenRectVertex(x+w, y, 1.f, 1.f),
ScreenRectVertex(x, y+h, 0.f, 0.f),
ScreenRectVertex(x+w, y+h, 0.f, 1.f),
};
glBindTexture(GL_TEXTURE_2D, texture.handle);
glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_handle);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices.data());
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}
/**
* Draws the emulated screens to the emulator window.
*/
@ -207,37 +196,22 @@ void RendererOpenGL::DrawScreens() {
glUseProgram(program_id);
// Set projection matrix
std::array<GLfloat, 3*2> ortho_matrix = MakeOrthographicMatrix((float)resolution_width, (float)resolution_height);
glUniformMatrix3x2fv(uniform_modelview_matrix, 1, GL_FALSE, ortho_matrix.data());
// Bind texture in Texture Unit 0
glActiveTexture(GL_TEXTURE0);
glUniform1i(uniform_color_texture, 0);
glEnableVertexAttribArray(attrib_position);
glEnableVertexAttribArray(attrib_texcoord);
const float max_width = std::max((float)VideoCore::kScreenTopWidth, (float)VideoCore::kScreenBottomWidth);
const float top_x = 0.5f * (max_width - VideoCore::kScreenTopWidth);
const float bottom_x = 0.5f * (max_width - VideoCore::kScreenBottomWidth);
for (int i = 0; i < 2; i++) {
ScreenInfo* current_screen = &screen_info[i];
glBindTexture(GL_TEXTURE_2D, current_screen->texture_id);
// Set sampler on Texture Unit 0
glUniform1i(sampler_id, 0);
glBindBuffer(GL_ARRAY_BUFFER, current_screen->vertex_buffer_id);
// Vertex buffer layout
const GLsizei stride = 5 * sizeof(GLfloat);
const GLvoid* uv_offset = (const GLvoid*)(3 * sizeof(GLfloat));
// Configure vertex buffer
glVertexAttribPointer(attrib_position, 3, GL_FLOAT, GL_FALSE, stride, NULL);
glVertexAttribPointer(attrib_texcoord, 2, GL_FLOAT, GL_FALSE, stride, uv_offset);
// Draw screen
glDrawArrays(GL_TRIANGLES, 0, 6);
}
glDisableVertexAttribArray(attrib_position);
glDisableVertexAttribArray(attrib_texcoord);
DrawSingleScreenRotated(textures[0], top_x, 0,
(float)VideoCore::kScreenTopWidth, (float)VideoCore::kScreenTopHeight);
DrawSingleScreenRotated(textures[1], bottom_x, (float)VideoCore::kScreenTopHeight,
(float)VideoCore::kScreenBottomWidth, (float)VideoCore::kScreenBottomHeight);
m_current_frame++;
}

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@ -7,12 +7,13 @@
#include "generated/gl_3_2_core.h"
#include "common/common.h"
#include "common/emu_window.h"
#include "core/hw/gpu.h"
#include "video_core/renderer_base.h"
#include <array>
class EmuWindow;
class RendererOpenGL : public RendererBase {
public:
@ -22,13 +23,6 @@ public:
/// Swap buffers (render frame)
void SwapBuffers();
/**
* Renders external framebuffer (XFB)
* @param src_rect Source rectangle in XFB to copy
* @param dst_rect Destination rectangle in output framebuffer to copy to
*/
void RenderXFB(const Common::Rect& src_rect, const Common::Rect& dst_rect);
/**
* Set the emulator window to use for renderer
* @param window EmuWindow handle to emulator window to use for rendering
@ -42,32 +36,21 @@ public:
void ShutDown();
private:
void InitOpenGLObjects();
void DrawScreens();
void UpdateFramerate();
/// Structure used for storing information for rendering each 3DS screen
struct ScreenInfo {
// Properties
int width;
int height;
int stride; ///< Number of bytes between the coordinates (0,0) and (1,0)
// OpenGL object IDs
GLuint texture_id;
GLuint vertex_buffer_id;
// Temporary
u8* flipped_xfb_data;
/// Structure used for storing information about the textures for each 3DS screen
struct TextureInfo {
GLuint handle;
GLsizei width;
GLsizei height;
};
/**
* Helper function to flip framebuffer from left-to-right to top-to-bottom
* @param raw_data Pointer to input raw framebuffer in V/RAM
* @param screen_info ScreenInfo structure with screen size and output buffer pointer
* @todo Early on hack... I'd like to find a more efficient way of doing this /bunnei
*/
void FlipFramebuffer(const u8* raw_data, ScreenInfo& screen_info);
void InitOpenGLObjects();
void DrawScreens();
void DrawSingleScreenRotated(const TextureInfo& texture, float x, float y, float w, float h);
void UpdateFramerate();
// Loads framebuffer from emulated memory into the active OpenGL texture.
static void LoadFBToActiveGLTexture(const GPU::Regs::FramebufferConfig& framebuffer,
const TextureInfo& texture);
EmuWindow* render_window; ///< Handle to render window
u32 last_mode; ///< Last render mode
@ -75,22 +58,15 @@ private:
int resolution_width; ///< Current resolution width
int resolution_height; ///< Current resolution height
// OpenGL global object IDs
GLuint vertex_array_id;
// OpenGL object IDs
GLuint vertex_array_handle;
GLuint vertex_buffer_handle;
GLuint program_id;
GLuint sampler_id;
std::array<TextureInfo, 2> textures;
// Shader uniform location indices
GLuint uniform_modelview_matrix;
GLuint uniform_color_texture;
// Shader attribute input indices
GLuint attrib_position;
GLuint attrib_texcoord;
struct : std::array<ScreenInfo, 2> {
ScreenInfo& Top() { return (*this)[0]; }
ScreenInfo& Bottom() { return (*this)[1]; }
} screen_info;
// "Flipped" framebuffers translate scanlines from native 3DS left-to-right to top-to-bottom
// as OpenGL expects them in a texture. There probably is a more efficient way of doing this:
u8 xfb_top_flipped[VideoCore::kScreenTopWidth * VideoCore::kScreenTopHeight * 4];
u8 xfb_bottom_flipped[VideoCore::kScreenBottomWidth * VideoCore::kScreenBottomHeight * 4];
GLuint attrib_tex_coord;
};

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@ -17,6 +17,10 @@ namespace VideoCore {
// 3DS Video Constants
// -------------------
// NOTE: The LCDs actually rotate the image 90 degrees when displaying. Because of that the
// framebuffers in video memory are stored in column-major order and rendered sideways, causing
// the widths and heights of the framebuffers read by the LCD to be switched compared to the
// heights and widths of the screens listed here.
static const int kScreenTopWidth = 400; ///< 3DS top screen width
static const int kScreenTopHeight = 240; ///< 3DS top screen height
static const int kScreenBottomWidth = 320; ///< 3DS bottom screen width