backends/opengl/graphics.cpp

// SPDX-License-Identifier: LGPL-2.1-or-later OR BSD-3-Clause
// SPDX-FileCopyrightText: 2004 - 2008 Olof Naessén and Per Larsson
// SPDX-FileCopyrightText: 2013 - 2026 Fifengine contributors
 
#include <fifechan/backends/opengl/graphics.hpp>
#include <fifechan/backends/opengl/image.hpp>
#include <fifechan/exception.hpp>
#include <fifechan/image.hpp>
 
#if defined(_WIN32)
    #include <windows.h>
#endif
 
#if defined(__APPLE__)
    #include <OpenGL/gl.h>
#else
    #include <GL/gl.h>
#endif
 
namespace fcn::opengl
{
    Graphics::Graphics()
    {
        setTargetPlane(640, 480);
    }
 
    Graphics::Graphics(int width, int height)
    {
        setTargetPlane(width, height);
    }
 
    Graphics::~Graphics() = default;
 
    void Graphics::_beginDraw()
    {
        glPushAttrib(
            GL_COLOR_BUFFER_BIT | GL_CURRENT_BIT | GL_DEPTH_BUFFER_BIT | GL_ENABLE_BIT | GL_FOG_BIT | GL_LIGHTING_BIT |
            GL_LINE_BIT | GL_POINT_BIT | GL_POLYGON_BIT | GL_SCISSOR_BIT | GL_STENCIL_BUFFER_BIT | GL_TEXTURE_BIT |
            GL_TRANSFORM_BIT);
 
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glLoadIdentity();
 
        glMatrixMode(GL_TEXTURE);
        glPushMatrix();
        glLoadIdentity();
 
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
 
        glOrtho(0.0, static_cast<double>(mWidth), static_cast<double>(mHeight), 0.0, -1.0, 1.0);
 
        glDisable(GL_LIGHTING);
        glDisable(GL_CULL_FACE);
        glDisable(GL_DEPTH_TEST);
        glDisable(GL_TEXTURE_2D);
 
        glEnable(GL_SCISSOR_TEST);
        glPointSize(1.0);
        glLineWidth(1.0);
 
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
        glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
 
        pushClipArea(Rectangle(0, 0, mWidth, mHeight));
    }
 
    void Graphics::_endDraw()
    {
        glMatrixMode(GL_MODELVIEW);
        glPopMatrix();
 
        glMatrixMode(GL_TEXTURE);
        glPopMatrix();
 
        glMatrixMode(GL_PROJECTION);
        glPopMatrix();
 
        glPopAttrib();
 
        popClipArea();
    }
 
    bool Graphics::pushClipArea(Rectangle area)
    {
        bool const result = fcn::Graphics::pushClipArea(area);
 
        glScissor(
            mClipStack.top().x,
            mHeight - mClipStack.top().y - mClipStack.top().height,
            mClipStack.top().width,
            mClipStack.top().height);
 
        return result;
    }
 
    void Graphics::popClipArea()
    {
        Graphics::popClipArea();
 
        if (mClipStack.empty()) {
            return;
        }
 
        glScissor(
            mClipStack.top().x,
            mHeight - mClipStack.top().y - mClipStack.top().height,
            mClipStack.top().width,
            mClipStack.top().height);
    }
 
    void Graphics::setTargetPlane(int width, int height)
    {
        mWidth  = width;
        mHeight = height;
    }
 
    void Graphics::drawImage(fcn::Image const * image, int srcX, int srcY, int dstX, int dstY, int width, int height)
    {
        auto const * srcImage = dynamic_cast<OpenGLImage const *>(image);
 
        if (srcImage == nullptr) {
            throwException("Trying to draw an image of unknown format, must be an OpenGLImage.");
        }
 
        if (mClipStack.empty()) {
            throwException(
                "The clip stack is empty, perhaps you called a draw function outside of _beginDraw() and _endDraw()?");
        }
 
        ClipRectangle const & top = mClipStack.top();
 
        dstX += top.xOffset;
        dstY += top.yOffset;
 
        // Find OpenGL texture coordinates
        float const texX1 = srcX / static_cast<float>(srcImage->getTextureWidth());
        float const texY1 = srcY / static_cast<float>(srcImage->getTextureHeight());
        float const texX2 = (srcX + width) / static_cast<float>(srcImage->getTextureWidth());
        float const texY2 = (srcY + height) / static_cast<float>(srcImage->getTextureHeight());
 
        glBindTexture(GL_TEXTURE_2D, srcImage->getTextureHandle());
 
        glEnable(GL_TEXTURE_2D);
 
        GLboolean const blendWasEnabled = glIsEnabled(GL_BLEND);
        if (blendWasEnabled == 0U) {
            glEnable(GL_BLEND);
        }
 
        // Draw a textured quad -- the image
        glBegin(GL_QUADS);
        glTexCoord2f(texX1, texY1);
        glVertex3i(dstX, dstY, 0);
 
        glTexCoord2f(texX1, texY2);
        glVertex3i(dstX, dstY + height, 0);
 
        glTexCoord2f(texX2, texY2);
        glVertex3i(dstX + width, dstY + height, 0);
 
        glTexCoord2f(texX2, texY1);
        glVertex3i(dstX + width, dstY, 0);
        glEnd();
        glDisable(GL_TEXTURE_2D);
 
        if (blendWasEnabled == 0U) {
            glDisable(GL_BLEND);
        }
    }
 
    void Graphics::drawPoint(int x, int y)
    {
        if (mClipStack.empty()) {
            throwException(
                "The clip stack is empty, perhaps you called a draw function outside of _beginDraw() and _endDraw()?");
        }
 
        ClipRectangle const & top = mClipStack.top();
 
        x += top.xOffset;
        y += top.yOffset;
 
        glBegin(GL_POINTS);
        glVertex2i(x, y);
        glEnd();
    }
 
    void Graphics::drawLine(int x1, int y1, int x2, int y2)
    {
        if (mClipStack.empty()) {
            throwException(
                "The clip stack is empty, perhaps you called a draw function outside of _beginDraw() and _endDraw()?");
        }
 
        ClipRectangle const & top = mClipStack.top();
 
        x1 += top.xOffset;
        y1 += top.yOffset;
        x2 += top.xOffset;
        y2 += top.yOffset;
 
        glBegin(GL_LINES);
        glVertex2f(x1 + 0.375F, y1 + 0.375F);
        glVertex2f(x2 + 1.0F - 0.375F, y2 + 1.0F - 0.375F);
        glEnd();
 
        glBegin(GL_POINTS);
        glVertex2f(x2 + 1.0F - 0.375F, y2 + 1.0F - 0.375F);
        glEnd();
 
        glBegin(GL_POINTS);
        glVertex2f(x1 + 0.375F, y1 + 0.375F);
        glEnd();
    }
 
    void Graphics::drawLine(int x1, int y1, int x2, int y2, unsigned int width)
    {
        // TODO(jakoch): Implement this function
    }
 
    void Graphics::drawPolyLine(PointVector const & points, unsigned int width)
    {
        // TODO(jakoch): Implement this function
    }
 
    void Graphics::drawBezier(PointVector const & points, int steps, unsigned int width)
    {
        // TODO(jakoch): Implement this function
    }
 
    void Graphics::drawRectangle(Rectangle const & rectangle)
    {
        if (mClipStack.empty()) {
            throwException(
                "The clip stack is empty, perhaps you called a draw function outside of _beginDraw() and _endDraw()?");
        }
 
        ClipRectangle const & top = mClipStack.top();
 
        glBegin(GL_LINE_LOOP);
        glVertex2f(rectangle.x + top.xOffset, rectangle.y + top.yOffset);
        glVertex2f(rectangle.x + rectangle.width + top.xOffset - 1.0F, rectangle.y + top.yOffset + 0.375F);
        glVertex2f(rectangle.x + rectangle.width + top.xOffset - 1.0F, rectangle.y + rectangle.height + top.yOffset);
        glVertex2f(rectangle.x + top.xOffset, rectangle.y + rectangle.height + top.yOffset);
        glEnd();
    }
 
    void Graphics::fillRectangle(Rectangle const & rectangle)
    {
        if (mClipStack.empty()) {
            throwException(
                "The clip stack is empty, perhaps you called a draw function outside of _beginDraw() and _endDraw()?");
        }
 
        ClipRectangle const & top = mClipStack.top();
 
        glBegin(GL_QUADS);
        glVertex2i(rectangle.x + top.xOffset, rectangle.y + top.yOffset);
        glVertex2i(rectangle.x + rectangle.width + top.xOffset, rectangle.y + top.yOffset);
        glVertex2i(rectangle.x + rectangle.width + top.xOffset, rectangle.y + rectangle.height + top.yOffset);
        glVertex2i(rectangle.x + top.xOffset, rectangle.y + rectangle.height + top.yOffset);
        glEnd();
    }
 
    void Graphics::drawCircle(Point const & p, unsigned int radius)
    {
        // TODO(jakoch): Implement this function
    }
 
    void Graphics::drawFillCircle(Point const & p, unsigned int radius)
    {
        // TODO(jakoch): Implement this function
    }
 
    void Graphics::drawCircleSegment(Point const & p, unsigned int radius, int sangle, int eangle)
    {
        // TODO(jakoch): Implement this function
    }
 
    void Graphics::drawFillCircleSegment(Point const & p, unsigned int radius, int sangle, int eangle)
    {
        // TODO(jakoch): Implement this method.
    }
 
    void Graphics::setColor(Color const & color)
    {
        mColor = color;
        glColor4ub(
            static_cast<GLubyte>(color.r),
            static_cast<GLubyte>(color.g),
            static_cast<GLubyte>(color.b),
            static_cast<GLubyte>(color.a));
 
        mAlpha = color.a != 255;
 
        if (mAlpha) {
            glEnable(GL_BLEND);
        }
    }
 
    Color const & Graphics::getColor() const
    {
        return mColor;
    }
 
    int Graphics::getTargetPlaneWidth() const
    {
        return mWidth;
    }
 
    int Graphics::getTargetPlaneHeight() const
    {
        return mHeight;
    }
} // namespace fcn::opengl