render: calculate texture coordinates based on scaling mode

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: Ie4e44a0cea68cbbee8122576c41aa4486a6a6964

src/render.c

@@ -8,6 +8,146 @@
 #include "../include/chroma.h"
 #include "../include/stb_image.h"
 
+// Convert filter quality enum to OpenGL parameters
+static void get_gl_filter_params(chroma_filter_quality_t quality,
+                                 GLint *min_filter, GLint *mag_filter) {
+  switch (quality) {
+  case CHROMA_FILTER_NEAREST:
+    *min_filter = GL_NEAREST;
+    *mag_filter = GL_NEAREST;
+    break;
+  case CHROMA_FILTER_LINEAR:
+    *min_filter = GL_LINEAR;
+    *mag_filter = GL_LINEAR;
+    break;
+  case CHROMA_FILTER_BILINEAR:
+    *min_filter = GL_LINEAR_MIPMAP_LINEAR;
+    *mag_filter = GL_LINEAR;
+    break;
+  case CHROMA_FILTER_TRILINEAR:
+    *min_filter = GL_LINEAR_MIPMAP_LINEAR;
+    *mag_filter = GL_LINEAR;
+    break;
+  default:
+    *min_filter = GL_LINEAR;
+    *mag_filter = GL_LINEAR;
+    break;
+  }
+}
+
+// Calculate texture coordinates based on scaling mode
+static void calculate_texture_coords(chroma_scale_mode_t scale_mode,
+                                     int image_width, int image_height,
+                                     int output_width, int output_height,
+                                     float tex_coords[8]) {
+  // Default texture coordinates (full texture)
+  float u1 = 0.0f, v1 = 0.0f; // top-left
+  float u2 = 1.0f, v2 = 1.0f; // bottom-right
+
+  switch (scale_mode) {
+  case CHROMA_SCALE_STRETCH:
+    // Use full texture, stretch to fit
+    u1 = 0.0f;
+    v1 = 0.0f;
+    u2 = 1.0f;
+    v2 = 1.0f;
+    break;
+
+  case CHROMA_SCALE_CENTER:
+    // Center image at original size
+    // Calculate how much of the texture to show
+    {
+      float image_aspect = (float)image_width / image_height;
+      float output_aspect = (float)output_width / output_height;
+
+      if (image_aspect > output_aspect) {
+        // Image is wider - fit width, show center portion vertically
+        float visible_height = (float)image_width / output_aspect;
+        float v_offset =
+            (image_height - visible_height) / (2.0f * image_height);
+        u1 = 0.0f;
+        v1 = v_offset;
+        u2 = 1.0f;
+        v2 = 1.0f - v_offset;
+      } else {
+        // Image is taller - fit height, show center portion horizontally
+        float visible_width = (float)image_height * output_aspect;
+        float u_offset = (image_width - visible_width) / (2.0f * image_width);
+        u1 = u_offset;
+        v1 = 0.0f;
+        u2 = 1.0f - u_offset;
+        v2 = 1.0f;
+      }
+    }
+    break;
+
+  case CHROMA_SCALE_FIT:
+    // Fit image within output, maintaining aspect ratio
+    {
+      float image_aspect = (float)image_width / image_height;
+      float output_aspect = (float)output_width / output_height;
+
+      if (image_aspect > output_aspect) {
+        // Image is wider - fit width, add borders top/bottom
+        float scaled_height = (float)output_width / image_aspect;
+        float v_border =
+            (output_height - scaled_height) / (2.0f * output_height);
+        u1 = 0.0f;
+        v1 = v_border;
+        u2 = 1.0f;
+        v2 = 1.0f - v_border;
+      } else {
+        // Image is taller - fit height, add borders left/right
+        float scaled_width = (float)output_height * image_aspect;
+        float u_border = (output_width - scaled_width) / (2.0f * output_width);
+        u1 = u_border;
+        v1 = 0.0f;
+        u2 = 1.0f - u_border;
+        v2 = 1.0f;
+      }
+    }
+    break;
+
+  case CHROMA_SCALE_FILL:
+  default:
+    // Fill entire output, crop if necessary
+    {
+      float image_aspect = (float)image_width / image_height;
+      float output_aspect = (float)output_width / output_height;
+
+      if (image_aspect > output_aspect) {
+        // Image is wider - crop left/right
+        float crop_width = image_height * output_aspect;
+        float u_crop = (image_width - crop_width) / (2.0f * image_width);
+        u1 = u_crop;
+        v1 = 0.0f;
+        u2 = 1.0f - u_crop;
+        v2 = 1.0f;
+      } else {
+        // Image is taller - crop top/bottom
+        float crop_height = image_width / output_aspect;
+        float v_crop = (image_height - crop_height) / (2.0f * image_height);
+        u1 = 0.0f;
+        v1 = v_crop;
+        u2 = 1.0f;
+        v2 = 1.0f - v_crop;
+      }
+    }
+    break;
+  }
+
+  // Set texture coordinates for quad (bottom-left, bottom-right, top-right,
+  // top-left)
+  tex_coords[0] = u1;
+  tex_coords[1] = v2; // bottom-left
+  tex_coords[2] = u2;
+  tex_coords[3] = v2; // bottom-right
+  tex_coords[4] = u2;
+  tex_coords[5] = v1; // top-right
+  tex_coords[6] = u1;
+  tex_coords[7] = v1; // top-left
+}
+
 // Vertex shader for simple texture rendering
 static const char *vertex_shader_source =
     "#version 120\n"
@@ -125,7 +265,7 @@ static int init_gl_resources(chroma_output_t *output) {
   glGenBuffers(1, &output->ebo);
 
   glBindBuffer(GL_ARRAY_BUFFER, output->vbo);
-  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_DYNAMIC_DRAW);
 
   glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, output->ebo);
   glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,
@@ -140,7 +280,8 @@ static int init_gl_resources(chroma_output_t *output) {
 
 // Create or update texture from image data
 static int update_texture_from_image(chroma_output_t *output,
-                                     chroma_image_t *image) {
+                                     chroma_image_t *image,
+                                     chroma_filter_quality_t filter_quality) {
   if (!output || !image || !image->loaded) {
     return CHROMA_ERROR_INIT;
   }
@@ -180,8 +321,12 @@ static int update_texture_from_image(chroma_output_t *output,
   // Set texture parameters
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+
-  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+  // Use configured filter quality
+  GLint min_filter, mag_filter;
+  get_gl_filter_params(filter_quality, &min_filter, &mag_filter);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, min_filter);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, mag_filter);
 
   // Upload texture data (always RGBA now)
   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image->width, image->height, 0,
@@ -503,7 +648,8 @@ int chroma_render_wallpaper(chroma_state_t *state, chroma_output_t *output) {
   }
 
   if (output->texture_id == 0) {
-    if (update_texture_from_image(output, output->image) != CHROMA_OK) {
+    if (update_texture_from_image(output, output->image,
+                                  output->filter_quality) != CHROMA_OK) {
       chroma_log("ERROR", "Failed to update texture for output %u", output->id);
       return CHROMA_ERROR_EGL;
     }
@@ -524,8 +670,25 @@ int chroma_render_wallpaper(chroma_state_t *state, chroma_output_t *output) {
   glBindTexture(GL_TEXTURE_2D, output->texture_id);
   glUniform1i(glGetUniformLocation(output->shader_program, "texture"), 0);
 
-  // Use cached VBO/EBO
+  // Calculate texture coordinates based on scaling mode
+  float tex_coords[8];
+  calculate_texture_coords(output->scale_mode, output->image->width,
+                           output->image->height, output->width, output->height,
+                           tex_coords);
+
+  // Create dynamic vertex data with calculated texture coordinates
+  float dynamic_vertices[] = {
+      // Position  Texcoord
+      -1.0f, -1.0f, tex_coords[0], tex_coords[1], // bottom-left
+      1.0f,  -1.0f, tex_coords[2], tex_coords[3], // bottom-right
+      1.0f,  1.0f,  tex_coords[4], tex_coords[5], // top-right
+      -1.0f, 1.0f,  tex_coords[6], tex_coords[7]  // top-left
+  };
+
+  // Update VBO with dynamic texture coordinates
   glBindBuffer(GL_ARRAY_BUFFER, output->vbo);
+  glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(dynamic_vertices),
+                  dynamic_vertices);
   glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, output->ebo);
 
   // Set vertex attributes