Add viewport

4 files changed, 53 insertions, 12 deletions

diff --git a/include/mgl/graphics/vertex.h b/include/mgl/graphics/vertex.h
index e4fef34..8cc2f25 100644
--- a/include/mgl/graphics/vertex.h
+++ b/include/mgl/graphics/vertex.h
@@ -14,6 +14,10 @@ typedef struct {
     mgl_color color;
 } mgl_vertex;
 
+/*
+    Note: this sends the vertices to the gpu everytime this is called. This should only be used for small lists of vertices
+    or if every vertex needs to change every frame. Use mgl_vertex_buffer instead if possible.
+*/
 void mgl_vertices_draw(mgl_context *context, const mgl_vertex *vertices, size_t vertex_count, mgl_primitive_type primitive_type);
 
 #endif /* MGL_VERTEX_H */
diff --git a/include/mgl/window/window.h b/include/mgl/window/window.h
index 297ccb9..8e3f626 100644
--- a/include/mgl/window/window.h
+++ b/include/mgl/window/window.h
@@ -14,12 +14,18 @@ typedef unsigned long mgl_window_handle;
 
 typedef struct mgl_window mgl_window;
 
+typedef struct {
+    mgl_vec2i position;
+    mgl_vec2i size;
+} mgl_view;
+
 struct mgl_window {
     mgl_window_handle window;
     GLXContext glx_context;
     mgl_vec2i size;
     /* relative to the top left of the window. only updates when the cursor is inside the window */
     mgl_vec2i cursor_position;
+    mgl_view view;
 };
 
 int mgl_window_create(mgl_window *self, const char *title, int width, int height);
@@ -32,4 +38,12 @@ void mgl_window_clear(mgl_window *self, mgl_color color);
 bool mgl_window_poll_event(mgl_window *self, mgl_event *event);
 void mgl_window_display(mgl_window *self);
 
+/*
+    The previous view is returned in |prev_view|. |prev_view| may be NULL.
+    This should be called every frame to retain the view.
+    Make sure to set the view back to |prev_view| after rendering items
+    inside the view.
+*/
+void mgl_window_set_view(mgl_window *self, mgl_view *new_view, mgl_view *prev_view);
+
 #endif /* MGL_WINDOW_H */
diff --git a/src/window/window.c b/src/window/window.c
index 9a650ae..44e0a23 100644
--- a/src/window/window.c
+++ b/src/window/window.c
@@ -32,10 +32,11 @@ static void mgl_window_on_resize(mgl_window *self, int width, int height) {
     mgl_context *context = mgl_get_context();
     self->size.x = width;
     self->size.y = height;
-    context->gl.glViewport(0, 0, self->size.x, self->size.y);
-    context->gl.glMatrixMode(GL_PROJECTION);
-    context->gl.glLoadIdentity();
-    context->gl.glOrtho(0.0, width, height, 0.0, -1.0, 1.0);
+
+    mgl_view view;
+    view.position = (mgl_vec2i){ 0, 0 };
+    view.size = self->size;
+    mgl_window_set_view(self, &view, NULL);
 }
 
 int mgl_window_create(mgl_window *self, const char *title, int width, int height) {
@@ -288,3 +289,14 @@ void mgl_window_display(mgl_window *self) {
     context->gl.glXSwapBuffers(context->connection, self->window);
 }
 
+void mgl_window_set_view(mgl_window *self, mgl_view *new_view, mgl_view *prev_view) {
+    if(prev_view)
+        *prev_view = self->view;
+
+    mgl_context *context = mgl_get_context();
+    self->view = *new_view;
+    context->gl.glViewport(new_view->position.x, self->size.y - new_view->size.y - new_view->position.y, new_view->size.x, new_view->size.y);
+    context->gl.glMatrixMode(GL_PROJECTION);
+    context->gl.glLoadIdentity();
+    context->gl.glOrtho(0.0, new_view->size.x, new_view->size.y, 0.0, 0.0, 1.0);
+}
diff --git a/tests/main.c b/tests/main.c
index 6a69866..99a8398 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -55,30 +55,41 @@ static void draw(mgl_window *window, void *userdata) {
     mgl_vertex_buffer_set_position(u->vertex_buffer2, (mgl_vec2f){ window->cursor_position.x, window->cursor_position.y + 500 });
     mgl_vertex_buffer_draw(context, u->vertex_buffer2, &u->font->texture);
 
+    mgl_vec2i view_size = {
+        .x = 200,
+        .y = 200
+    };
+
+    mgl_view prev_view;
+    mgl_view new_view = {
+        .position = { window->size.x/2 - view_size.x/2, window->size.y/2 - view_size.y/2 },
+        .size = view_size
+    };
+    mgl_window_set_view(window, &new_view, &prev_view);
     mgl_vertex vertices[4] = {
         (mgl_vertex){
-            .position = {window->cursor_position.x, 0.0f},
+            .position = {-new_view.position.x + window->cursor_position.x, -new_view.position.y + window->cursor_position.y},
             .texcoords = {0.0f, 0.0f},
-            .color = {0, 255, 0, 255}
+            .color = {255, 0, 0, 255}
         },
         (mgl_vertex){
-            .position = {window->cursor_position.x + 100.0f, 0.0f},
+            .position = {-new_view.position.x + window->cursor_position.x + 400.0f, -new_view.position.y + window->cursor_position.y},
             .texcoords = {0.0f, 0.0f},
             .color = {0, 255, 0, 255},
         },
         (mgl_vertex){
-            .position = {window->cursor_position.x + 100.0f, 100.0f},
+            .position = {-new_view.position.x + window->cursor_position.x + 400.0f, -new_view.position.y + window->cursor_position.y + 400.0f},
             .texcoords = {0.0f, 0.0f},
-            .color = {0, 255, 0, 255},
+            .color = {0, 0, 255, 255},
         },
         (mgl_vertex){
-            .position = {window->cursor_position.x, 100.0f},
+            .position = {-new_view.position.x + window->cursor_position.x, -new_view.position.y + window->cursor_position.y + 400.0f},
             .texcoords = {0.0f, 0.0f},
-            .color = {0, 255, 0, 255}
+            .color = {255, 255, 0, 255}
         }
     };
-
     mgl_vertices_draw(context, vertices, 4, MGL_PRIMITIVE_QUADS);
+    mgl_window_set_view(window, &prev_view, NULL);
 }
 
 int main(int argc, char **argv) {